If there’s a quintessential dish from chef Nadiya Hussain — the Great British Baking Show winner — it’s probably the samosa pie with turmeric crust from the very first episode of her solo cooking show Nadiya’s Family Favourites. Meant to be unmolded for maximum impact, the pie stands impossibly tall and doesn’t crumble, even when sliced.

Understanding how and when to use hot water can transform the way we cook and bake. Found in baked goods across the world, hot water can yield softer, fluffier breads; and create stunning pie crusts like Hussain’s.

“When you heat a wet starch above 140 degrees Fahrenheit, the starch granules begin to swell quickly into a meshlike network that traps water in the dough even as it cooks,” said Dan Souza, the editor of Cook’s Illustrated.

This process is called gelatinization, and it’s what happens when you use boiling water to make the silky, supple dumpling doughs used all over Europe and Asia. It’s a part of French pâte à choux, in which water and flour are cooked together to form the foundational pastry for both cream puffs and gougères.

Gelatinization can also be used to bind breads made with flour that doesn’t contain gluten, Souza said, like tapioca or cornmeal. It’s even an added benefit of nixtamalization, the process of simmering dried corn kernels in an alkaline solution to prepare them for grinding and mixing into masa. Hot water helps hydrate the coarse flours and dried fruits, or diffuse flavors and colors from grated beets or ground turmeric, which is what gives Hussain’s golden pie crust its distinctive hue.

Jaisinghani has noticed that hot water also makes her baked goods a little fluffier because it speeds up the reaction time of chemical leaveners like baking soda or baking powder. With hot water, she said, there’s a bit more lift happening as you slide them into the oven.

Jaisinghani was a microbiologist before she became a restaurateur but says a lot of these science-based techniques were what she was taught as a child in India.

“Most of this never made sense to me until I figured out the why,” she said.

SAMOSA PIE
By: Nadiya Hussain, adapted by Rachel Wharton

For the Samosa Filling:

• 5 tablespoons olive oil
• 1 heaping cup white onion,finely chopped
• Kosher salt
• 1 teaspoon ground ginger
• 1 tablespoon granulated garlic
• 1 tablespoon cumin seeds
• 2 teaspoons red pepper flakes
• 1 pound ground lamb
• 1 pound red or gold potatoes, peeled, cut into 1/2-inch cubes
• 1 cup frozen peas
• 2 tablespoons cornstarch whisked into 1/4 cup cold water
• 3/4 cup loosely packed, finely chopped cilantro leaves

For the Dough:

• 2 1/3 cups all-purpose flour (see Tip)
• 1 teaspoon kosher salt
• 1 teaspoon ground turmeric
• 1/3 cup vegetable shortening
• 1 large egg, beaten, for glazing

Make the filling:

Heat the oil in a large skillet over medium heat. Add the onion and 1 1/2 teaspoons salt and cook, stirring occasionally, until the onion is soft and translucent, about 5 minutes. Stir in the ginger, garlic, cumin and red pepper flakes, and cook until fragrant, a minute or two.

Add the lamb and cook, stirring occasionally and breaking into small pieces, until it is just cooked through, 6-8 minutes. Stir in the potatoes, cover, reduce the heat to medium-low and let everything steam, stirring once halfway through, until the potatoes are just soft, about 20 minutes.

Uncover, stir in the peas and cook until just heated through, a minute or two. Stir in the cornstarch slurry, then turn off the heat and stir in the cilantro. Season to taste with salt, and let cool completely before building the pie.

When the filling has cooled, arrange an oven rack in the lowest position and heat oven to 400 degrees.

Make the pastry: Whisk the flour, salt and turmeric in a large heatproof mixing bowl. Create a small well in the center.

In a small pot, bring 2/3 cup plus 1 tablespoon water and the shortening to a boil over medium heat. As soon as the shortening has melted completely into the boiling water, pour the mixture into the well in the flour. Use a wooden spoon to quickly stir the hot water into the flour, making sure everything gets wet. As soon as it is cool enough to handle, knead the dough with your hands in the bowl or on a clean work surface until it comes together in a smooth ball.

Wrap a third of the dough in plastic wrap and set aside. Roll the remaining dough into an 11-inch circle (about 1/8-inch thick) between two large pieces of plastic wrap or parchment paper. Remove one piece of wrap or paper and flip the pastry into an 8-inch springform pan, centering it and using your hands to gently press it into the bottom and against the sides. The dough should be supple and smooth enough that, if you tear it, you can easily patch any holes.

Discard the wrap or paper. Add the filling and use the back of a spoon to press it in and level the surface. There should be a 1/2-inch rim of dough above the filling. Brush it with the beaten egg.

Roll the reserved dough into a 9-inch circle (about 1/8-inch thick) between two pieces of plastic wrap or parchment paper. Remove one piece of wrap or paper and flip the pastry over the filling, centering it and pushing it down so that it fits snugly.

The edge of the top crust will overlap the edge of the bottom crust. Press these two edges together gently against the side of the pan.

Using a knife, trim the top of the combined edges to create an even border around the pan, then use your fingers to crimp that bit of dough back down into the pie, sealing the edges.

Cut a hole in the center of the pie to allow air to escape, brush the top with egg and bake until the top is deep golden brown and firm, 1 hour to 1 hour, 15 minutes, rotating the pan halfway through. Let cool in the pan on a rack for at least 1 1/2 hours before unmolding and serving.

Total time: 2 1/2 hours, plus cooling; serves 6-8.

Tip: The original recipe calls for 2 cups all-purpose flour and 1/3 cup bread flour. If you have both on hand, you can use them, but this dough works just as well with only all-purpose flour.