-Melt the butter in a heavy-bottomed saucepan over medium heat. Stir in the flour and cook, stirring occasionally, for 1 minute. Slowly add the warmed milk and whisk to remove the lumps. As the mixture heats, it will thicken. Add the cheese, salt, and cayenne pepper as the mixture thickens. Continue whisking until the cheese sauce is thick and creamy. Keep warm, but do not cover. *Note - if you're making the cheese sauce in advance, it will become firm once cool. To make the sauce pourable, reheat gently on the stovetop or in a microwave on low power.
-Place the broccoli florets in a microwave-safe dish and microwave for 2-3 minutes on medium power. Add ½ teaspoon salt, ¼ teaspoon pepper, and olive oil. Stir well to combine. Set aside to cool slightly.
-Use the rolling pin to gently and evenly roll the pie dough(making it slightly larger in circumference) out onto a lightly sprayed sheet of parchment paper. Carefully transfer the pie dough and paper to a baking sheet. *Note - this can be done by evenly pulling the parchment paper onto the baking sheet.
-Place about 2 tablespoons of the cheese sauce in the middle of the pie dough and use a spoon to spread it into a circle of the dough, leaving the edges clean. Place the precooked broccoli on top of the cheese sauce and spread it out slightly, leaving about 2" of plain pie dough.
-Gently pull the pie dough edges up and over the broccoli, making folds (or pleats) as you go.
-Mix the egg and water in a small bowl with a fork. Brush the egg wash evenly over the top of the pie dough. Sprinkle the top of the dough with the sesame seeds (if using) and a pinch of black pepper.
-Bake in a preheated oven for 30-35 minutes or until the pie dough is lightly browned. -Serve hot with the warmed cheese sauce.
Notes
Store any leftovers in an airtight container in the refrigerator for up to 5 days.Not recommended for freezing.