Cheddar and Onion Pie
For the Cheese and Onion Pie Filling
- 1/4 cup unsalted butter, or half a stick
- 6 onions, thinly sliced
- 1 teaspoon kosher salt
- 1 teaspoon freshly ground black pepper
- 3/4 cup water
- 1 1/2 pounds grated Cheddar cheese
- 2 whole eggs
- 5 tablespoons sour cream
- 2 teaspoons British style prepared mustard
For the Hot Water Pastry
- 12 3/4 ounces (or 3 cups) all-purpose flour
- 1 generous tablespoon dried mustard powder
- 3/4 teaspoon kosher salt
- 1 cup unsalted butter, or 2 sticks
- 1/3 cup whole milk
- 1 egg, beaten with 1 tablespoon whole milk
To Make the Filling:
Melt the butter in a 3 quart saucepan over low heat. Toss in the thinly sliced onion, salt, and pepper to coat evenly. Cook the onions for 4 minutes, stirring frequently. Pour in the water, stir well, and raise the heat to medium and cook, stirring often, until the onions are soft but not golden, about 6 to 8 more minutes. Set aside to cool to room temperature or cover and chill in the refrigerator for up to 2 days.In a mixing bowl, stir together the cooled onions, grated cheese, eggs, sour cream, and British mustard until evenly combined. Set aside the filling to make your pastry dough.
To Make and Fill Your Crust:
Preheat oven to 375°F. Line a springform pan or casserole dish with parchment paper and set aside.
Be certain your filling is ready to go. In a large mixing bowl, whisk together the all purpose flour, mustard powder, and kosher salt. Make a well in the center of the flour and set aside.
Place a medium sized saucepan over medium heat. Gently bring the milk and butter to a simmer. Pour this hot liquid into the flour well. Use a heat-proof spatula to mix together until a shaggy dough mass forms. Transfer the dough to a lightly floured surface and knead until smooth, about 2-3 minutes. Divide dough into two pieces. While the dough is still hot, roll each piece between two pieces of parchment paper or plastic wrap to about the size of the base of your pan. Ease one of the rounds of dough into your prepared pan. Starting at the center of the dough press outward, gently working the dough outward and up the sides of the pan. Don't worry if it tears a bit, you can patch it with excess dough.
Scrape the filling into the crust, level gently, and position the second crust over the filling, trimming the excess away and pinching the seams where the bottom and top crusts meet together. Brush the top crust with the egg wash and use a sharp knife to cut three vent holes. Place your tart pan or pie crust on a rimmed sheet pan and bake for 60 to 70 minutes or until quite a deep glossy brown and the filling is bubbling up through the vent holes.
Allow to cool until just warm or room temperature before slicing. Leftovers hold well in the refrigerator for up to a week.