Free-form pies have always been a way to turn a little into a lot.

Empanadas, samosas, knishes, turnovers, strudels, galettes and even kolaches are all slightly (or not so slightly) different variations on handpies, but they all share some commonalities that Cathy Barrow explores in her latest book, “When Pies Fly.”

“These are pies that you could make anywhere you have an oven,” she says, no special pie pan needed.

Barrow, who lives in the Washington, D.C., area and became known for her 2014 cookbook, “Mrs. Wheelbarrow’s Practical Pantry,” teaches pastry and pie classes across the country, and all of her students want to learn the mysteries of pie dough.

“The sentence that reads, ‘Mix the flour and butter until it looks like fill in the blank. Peas, damp sand, cornmeal.’ It drove me insane because I never knew what it meant,” she says.

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Her solution is twofold. First, for a traditional pie dough crust, simply pulse the ingredients in a food processor 15 times. “For many people, that alone has solved their dough phobia.”

But the second tip is to encourage people to make different kinds of dough, including puff pastry and strudel.

“For a long time, I had in my head that, in order to make strudel, you needed to have 30 able-bodied large relatives to stand around a table the size of a basketball court,” she says. But in reality, she discovered that the dough is easy to handle and is relatively forgiving, once you get used to stretching the dough with your knuckles, kind of like pizza dough.

Most Americans are familiar with sweet strudels, but savory strudels are common in Europe, and because the master dough recipe doesn’t have any sugar in it, you can easily make a batch and use some of it for a savory dish and another for something sweet.

In fact, all of the fillings in “When Pies Fly” can go with any of the doughs. Barrow says she developed the recipes knowing that readers might like the filling in one recipe, but not the form.

If you’ve been watching “The Great British Baking Show,” and wondering how to make a rough puff, she has a 15 minutes recipe that can be used in dozens of variations.

Some of the pies in her book are like adult Hot Pockets, but without the funky smell and weirdly colored cheese. The broccoli cheddar hand pies, for instance, are the perfect mid-afternoon treat, she says, just make sure you chop the broccoli into small pieces so you don’t end up with a lumpy pie.

She offers other tips that will help beginners and seasoned pie-makers alike.

“Most people underseason their fillings,” she says. “Dough is like bread, so you need to zip up the fillings with a little extra lemon juice, salt or chile powder.”

All the Thanksgiving leftovers are perfect for an open-faced galette, she says. Mashed potatoes, stuffing, turkey, corn, Brussels sprouts, green beans and even cranberry sauce can be mixed together to create a samosa filling or a strudel.

If your filling looks a little dry, consider adding a tablespoon or two of cream cheese. “Just two ounces will make it all creamy and pull it all together,” she says. “It’s luscious.”

Don’t fear frozen fruit, either. Strawberries, blueberries and blackberries in the freezer are usually a lot nicer than the strawberries in the produce section. And the best thing about using frozen fruit is that you can use it while it’s still frozen.

Raw apples tossed in a little sugar and cinnamon make an easy apple strudel, but she also makes one with pears, sweet potatoes, pistachios and port-soaked prunes that straddles the fence between sweet and savory. “I can’t tell you if it’s the dessert or cheese course,” she says.

Barrow says she understands if, like Nora Ephron, you are in the camp of people who will never ever make your own pie dough. “I just want you to make pie.”

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Kale, Mushroom and Gruyère Strudel

A decadent and worthy way to get your veggies, this is a spectacular dish for buffets and potlucks, or served as a vegetarian side in a meat-heavy dinner (think Thanksgiving). The mushrooms are the star here and I rely on a pan-roasting technique for deep flavor and a texture that is never waterlogged. If you are a forager, or know one, using chanterelles or morels would be sublime.

— Cathy Barrow

1 recipe Pulled Dough for Strudel, below

2 tablespoons olive oil

8 ounces cremini mushrooms, stemmed and sliced 1/4-inch thick

1 medium onion, diced (about 1 cup)

8 ounces lacinato kale, ribs removed and leaves roughly chopped (about 3 cups)

1/4 cup chopped flat-leaf parsley

1 teaspoon fresh thyme leaves

1 1/2 teaspoons kosher salt

3/4 teaspoon freshly ground black pepper

1 large egg, beaten

6 ounces Gruyère cheese, shredded

4 tablespoons unsalted butter, melted

1/4 cup dry bread crumbs

Bring the strudel dough to room temperature for 1 hour before stretching, keeping it in the ziptop bag until ready to use. Heat the oven to 400 degrees and place a rack in the lower third of the oven. Line a baking sheet with parchment.

Heat the oil in a large heavy skillet over high heat. When the oil is shimmering, add the mushroom slices and reduce the heat to medium-high. Do not mess with the mushrooms. Let them pan-roast and get deeply browned, 6 to 8 minutes, before giving the pan a hard shake so they release. Then turn the mushrooms and roast for another 4 to 5 minutes, until well browned and crisped. Add the onion, stir well, and cook until wilted, 5 or 6 minutes. Add the chopped kale and cook for another 3 minutes, until the kale has collapsed but is still brightly colored. Stir in the parsley, thyme, salt and pepper. Spread the mixture across a baking sheet to cool. (Freeze or refrigerate to speed the cooling process.) Once thoroughly cool, return to a bowl, and stir in the egg and cheese.

Prepare the work surface and stretch the strudel dough to 20 inches by 24 inches, until it’s possible to “read a newspaper through it” or some close approximation of that idea. The whole process doesn’t take long at all, just 5 minutes or so, once you’ve done it a few times.

Pat the stretched dough into shape and then, using scissors or your fingertips, tear or cut away the thick edges and discard. Carefully swab the dough with about 2 tablespoons of the melted butter.

Add 1 tablespoon of the melted butter to the bread crumbs and stir well. Sprinkle the bread crumbs generously over the dough, leaving a 2-inch border. Transfer the kale filling to the dough using your hands and shape it into a log about 2 inches from a shorter edge.

Begin rolling by lifting and pulling the bare 2-inch edge of the dough over the kale log. Tuck in the sides and, using the strudel cloth, lift and roll the strudel into a tight log with the thin layers of strudel dough encasing the filling. The goal is to make this log firm and tight, not loose and sloppy.

Use the cloth to transfer the strudel to the prepared baking sheet, seam side down.

Brush the top and sides of the strudel with the remaining melted butter. Bake for 20 to 25 minutes, until golden brown. Cool in the pan for 10 minutes before slicing and serving.

If serving later, reheat for a few minutes in a 350 degrees oven. Serves 8 to 10.

— From “When Pies Fly: Handmade Pastries from Strudels to Stromboli, Empanadas to Knishes” by Cathy Barrow (Grand Central Publishing, $30)

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Pulled Dough for Strudel

Strudel dough is not rolled out with a pin, but stretched. Because of this, the dough needs to be very elastic, requiring well-developed gluten which means active, extensive kneading. Kneading can be tiresome, so do as generations of Germans, Austrians and Alsatians have done, and slap the dough on the counter with vigor instead. Just lift it up and slap it down, turn, fold and do it again. And again. In fact, most classic strudel dough recipes include the direction to lift and slap the dough on the counter 100 or more times. It’s a great way to get out that daily “grrr,” and a good workout for the arms. But if you aren’t feeling the slapping, you can knead in the usual way, folding and pushing the dough away from you, and then turning it 90 degrees and continuing the fold and push and turn action for 10 minutes. Alternatively, put the organized dough ball in the stand mixer and let the machine do the work for 10 full minutes.

— Cathy Barrow

1 1/4 cups all-purpose flour

1/4 teaspoon kosher salt

3 tablespoons grapeseed or canola oil

1/3 cup cool water

In a wide bowl, using a table fork, stir together the flour and salt. Make a well in the center and pour in the oil. Gather the flour into the oil with the fork. Pour in the water slowly, continuing to use the fork to incorporate the flour, until the dough is shaggy and wet. It will look impossible and you will be unhappy with me, but please persist.

Let go of the fork, lightly flour your hands, and work inside the bowl to gather the dough (which, admittedly, is more like batter). Just lift and turn, fold and lift, and unbelievably the dough will begin to feel silky and smooth and come together after 5 minutes or so. It’s a miracle.

Move the dough ball onto a very lightly floured counter and knead for 10 minutes; or slap it vigorously 100 times; or place the dough ball in the stand mixer and, with the dough hook in place, let the mixer knead the dough for 10 minutes.

Lightly coat the inside of a ziptop bag with cooking spray and place the dough in the bag. After a 30-minute rest on the counter, seal the bag and refrigerate overnight before stretching the dough.

Strudel dough can be refrigerated for up to 2 days and cannot be successfully frozen. Makes 1 strudel sheet, about 20 by 24 inches when pulled.

— From “When Pies Fly: Handmade Pastries from Strudels to Stromboli, Empanadas to Knishes” by Cathy Barrow (Grand Central Publishing, $30)