- 1 1/4 cups all-purpose flour
- 1/2 teaspoon salt
- 1/2 teaspoon white sugar
- 1/2 cup cold unsalted butter, cut into small pieces
- 2 tablespoons ice water, or as needed
- 1 large yellow onion, sliced
- 1 (8 ounce) package shredded Cheddar cheese
- 1/2 cup shredded mozzarella cheese
- 1/4 cup grated Parmesan cheese
- 3 hard-boiled eggs, peeled and sliced
- 1/2 cup half-and-half
- freshly ground black pepper to taste
- 3/4 cup finely crushed buttery round crackers
- 1/4 cup butter, melted
- Whisk flour, salt, and sugar in a bowl; work 1/2 cup unsalted butter pieces into dry ingredients with your fingers until flour mixture looks like coarse meal. Mix ice water into dough a little at a time until it just holds together. Form into a ball and press dough down to form a flat disk; wrap in plastic wrap and refrigerate at least 1 hour.
- Preheat oven to 350 degrees F (175 degrees C).
- Roll dough out to a circle on a floured work surface and fit crust into a 9-inch pie dish; crimp the edges.
- Place onion slices into a saucepan, cover with water, and bring to a boil; reduce heat to medium and boil until onion is translucent, about 5 minutes. Drain and cool onion slices; spread into bottom of pie crust and top with Cheddar, mozzarella, and Parmesan cheeses in layers. Spread egg slices over cheese. Pour half-and-half over filling and sprinkle with black pepper.
- Mix buttery round cracker crumbs and 1/4 cup melted butter in a bowl; sprinkle crumb mixture evenly over pie.
- Bake in the preheated oven until browned, about 40 minutes.