Mushroom Quiche

In a food processor, combine 1.75 cups flour and 0.5 or 1/2 teaspoon salt. Cut the 12 tablespoons chilled butter into 1/2-inch pieces, add it to the flour, and pulse until the butter is about the size of large peas.

Combine 3 tablespoons sour cream and 1/3 cup ice water. Add the mixture gradually to the flour and pulse until large clumps form. If the dough is still dry, add 1–2 tablespoons additional ice water as needed.

Shape the dough into a 6-inch disk, wrap it in plastic, and refrigerate for 1–2 hours. It can be refrigerated for up to 24 hours; if very firm, let it stand at room temperature for about 15 minutes before rolling.

Grease a deep pie or quiche pan. Roll the chilled dough on a generously floured surface into approximately a 15-inch circle,1/4 inch thick. Fit it into the pan, trim excess dough, patch any cracks, and refrigerate for 20–30 minutes.

Preheat the oven to 375°F. Line the chilled crust with parchment paper or foil and fill it completely with dry beans or pie weights. Blind-bake for 15–20 minutes, then carefully remove the weights and lining.

The original ingredient list includes 1 lightly beaten egg white but does not specify its use in the directions. To incorporate it, lightly brush the warm pre-baked crust with the beaten egg white to help seal the surface before adding the filling.

Reduce the oven temperature to 325°F. Finely chop the 2 shallots and slice the 8 oz mushrooms.

Melt 2 tablespoons butter in a sauté pan. Add the sliced mushrooms and chopped shallots and cook until softened and all mushroom liquid has evaporated. Add 0.25 or 1/4 cup white wine, if using, and cook for about 1 minute, until evaporated. Season with 0.25 or  1/4 teaspoon salt and 0.25 or  1/4 teaspoon black pepper.

Lightly beat the 7 eggs. Whisk them with 4 cups half-and-half or milk and 1 pinch nutmeg. Alternatively, use 2 cups heavy whipping cream plus 2 cups milk. Stir the cooked mushroom-and-shallot mixture into the custard.

Grate 1/2–3/4 cup Gruyère or Swiss cheese. Sprinkle half of the cheese over the bottom of the pre-baked crust.

Pour the mushroom custard into the crust and sprinkle the remaining grated cheese evenly over the top.

Place the quiche pan on a baking sheet and bake at 325°F for 75–90 minutes, or until the custard is set, puffed, and lightly browned. Let it rest before slicing. Serve warm or cooled; it can also be refrigerated and reheated the following day.