Ham and Leek Quiche

Ingredients
1 9-in. frozen deep-dish piecrust shell
2 tablespoons unsalted butter
2 cups packed sliced Swiss chard leaves (from a 5-oz.bunch), tough ribs removed
1 medium leek, white and pale green parts sliced (1 cup)
4 large eggs
1 ⅓ cups whole buttermilk
½ teaspoon kosher salt
¼ teaspoon freshly ground black pepper
4 ounces Gruyère cheese, shredded (about 1 cup)
⅔ cup chopped leftover or deli ham
Directions
Step 1: Preheat oven to 375°F. Place pie crust on a baking sheet. Melt butter in a large skillet over medium. Add chard and leek; cook, stirring occasionally, until mixture is tender, 6 to 8 minutes. Remove from heat. Let cool for 5 minutes.
Step 2: Whisk eggs, buttermilk, salt, and pepper in a large bowl. Add cooled leek mixture, cheese, and ham; fold until combined. Pour into piecrust.
Step 3: Bake until center of quiche is just set, 40 to 45 minutes. Remove from oven. Let cool for 10 to 15 minutes before slicing.