- Make the dough: Pulse flour, salt, and sugar in food processor. Slowly add butter into mixture until it resembles coarse meal. Add up to 6 tablespoons ice water, until dough just begins to hold together.
- Drop dough onto flour-dusted work surface. Press firmly into a rough ball and knead slightly. Flatten into disk and wrap tightly in plastic. Refrigerate for 2 hours.
- After dough has chilled, preheat oven to 400 degrees. Roll out dough and place in a buttered pie tin with removable bottom. Cover with buttered foil and blind bake 20 to 25 minutes. Remove foil and brush with egg. Bake 2 more minutes.
- Make the filling: Boil bacon in water for about 5 minutes. Drain, return to pan, and cook over medium heat until lightly browned, about 3 minutes. Drain on a paper towel-lined plate. Arrange bacon in pie crust. Sprinkle gruyère to cover.
- Whisk eggs with cream and salt. Whisk in nutmeg and pepper. Pour mixture into crust and bake until custard is puffed, golden, and just set in center, about 30 to 35 minutes.