Mushroom-Shallot Quiche Recipe

Ingredients

• 1 1/2 cups all purpose flour
• 1 teaspoon salt
• 1 teaspoon sugar
• 1/2 cup (1 stick) chilled unsalted butter, cut into 1/2-inch cubes
• 1 large egg
• 1 teaspoon cold water
• 1 large egg white, lightly beaten
• 1 1/2 tablespoons unsalted butter
• 1/3 cup chopped shallots (about 2 medium)
• 1/2 pound mushrooms, cut into 1/4-inch slices
• 5 teaspoons chopped fresh thyme, divided
• 3/4 cup whipping cream
• 2 large eggs
• Pinch of salt
• Pinch of ground black pepper
• 2 green onions (white and pale green parts only), thinly sliced
• 2 tablespoons finely grated Gruyère cheese