Grilled Flatbread with Apples, Bacon, and Leeks

Ingredients

• 2 tablespoons unsalted butter
• 2 tablespoons all-purpose flour
• 1 cup whole milk
• 1/2 cup grated white cheddar
• 1/2 cup grated Gruyére
• 1 1/2 tablespoons sour cream
• Sprinkle of nutmeg
• Kosher salt
• Freshly ground pepper
• 8 slices thick-cut bacon, cut into bite-size pieces
• 2 leeks, washed, trimmed, and thinly sliced crosswise
• 2 Granny Smith Apples (or other tart apples), peeled and chopped into 1/2'' pieces
• 1 tablespoon fresh sage, finely minced
• 1 tablespoon fresh thyme, finely minced
• 1 teaspoon fresh rosemary, finely minced
• 1 room temperature Pizza Dough, bought from local pizzeria,