Melt butter in a skillet over medium heat.

Sauté sliced portabella mushrooms until browned and softened.

Add minced garlic and cook for 2 minutes until fragrant.

Stir in thinly sliced sun-dried tomatoes and set aside.

Prepare the pastry: Mix flour and salt in a bowl.

Cut in chilled butter and vegetable shortening with a pastry cutter until crumbly.

Add ice-cold milk, one tablespoon at a time, mixing lightly until moistened, adding more if necessary.

Gather dough into a ball and roll out between two sheets of wax paper.

Peel off one sheet of wax paper and place pastry onto an 8 or 9-inch pie plate.

Peel off the second sheet of wax paper and fit the pastry nicely into the shell.

Crimp the edges of the pastry.

Paint the edges with a small amount of unbeaten egg white to prevent soggy crust.

Alternatively, use a prepared pie crust and paint edges with egg white.

Prepare the custard: Beat together whipping cream, egg yolks, salt, cayenne pepper, and freshly grated nutmeg.

Stir in slivered fresh basil.

Fill the unbaked pie shell with the sautéed mushroom mixture.

Pour the custard over the mushroom mixture.

Bake in a preheated 375°F (190°C) oven for 40 to 45 minutes, or until the custard is set and deeply browned.

Let the quiche set for 5 minutes before cutting and serving.