Галета с мускатной тыквой

Ингредиенты

• 1 1/4 cups all-purpose flour
• 1 stick cold unsalted butter, cut into 1/2-inch cubes
• 1 tablespoon chopped sage leaves
• 1/2 teaspoon fine sea salt
• 4 to 6 tablespoons ice-cold water
• 1 large egg, lightly beaten
• 1 (2-pound) butternut squash, peeled, seeded, and cut into 2- by 1/4-inch slices (4 cups)
• 1/2 teaspoon fine sea salt
• 3 tablespoons olive oil, divided
• 2 leeks (white and pale green parts only), thinly sliced crosswise
• 6 ounces soft mild goat cheese, crumbled