For the cheese and onion filling
2 tablespoons unsalted butter
1 1/2 large onions, finely chopped
2 tart apples, peeled, cored and cut into very thin slices
2 1/2 cups strong farmhouse-style cheddar cheese, coarsely grated
3 large eggs
1/4 cup heavy cream
1 sprig thyme (leaves only), finely chopped
Pinch (or two or three) cayenne pepper
Freshly ground black pepper
Make the pie crust, separate into two parts, with one slightly larger. Wrap both up and chill for 30 minutes at least. If you haven't done it before (or desire better results) - check out this excellent step by step at my favorite food blog, Smitten Kitchen.
For the cheese and onion filling: In a large skillet over medium heat, melt the butter. Add the onion and cook for 20 to 30 minutes or until softened. Add the apples and cook for a few minutes; they should not lose their texture. Transfer to a large bowl and let cool to room temperature, then add the grated cheese, 2 of the eggs, cream, thyme and salt and peppers to taste, mixing well. Set aside.
To assemble: Preheat the oven to 425 degrees. Have ready a lightly greased 9-inch pie pan.
On a lightly floured work surface, roll out the larger piece of dough to a 10-inch round and transfer it to the pie pan. In a small bowl, beat the remaining egg and moisten the edges of the dough with a bit of the egg. Re-flour the work surface and roll out the remaining dough in the same manner, but slightly smaller. Add the cheese and onion filling and top with the remaining rolled-out dough, crimping the top and bottom crusts together at the edges. Brush the top crust with the beaten egg. Add decorative slits in the top crust in your favorite festive shape with a sharp paring knife. Bake for 30 minutes, until golden brown. Let cool 15 minutes before serving.
(recipe adapted from Smitten Kitchen link above and the Washington Post - original here.)