Preheat the oven:
Preheat your oven to 180°C (350°F) and grease a 12-cup muffin tin.

Make the cheese sauce:
In a saucepan, melt butter over medium heat. Stir in the flour and cook for 1–2 minutes to form a roux. Slowly add the milk while whisking constantly, then cook until the sauce thickens, about 4–5 minutes.
Stir in the cheddar, mozzarella, mustard powder (if using), garlic powder, salt, and pepper. Once the cheese is melted and the sauce is smooth, remove from heat.

Combine pasta and sauce:
Stir the cooked macaroni into the cheese sauce, then add the beaten egg. Mix well to coat all the pasta.

Fill the muffin tin:
Spoon the mac and cheese mixture into the muffin cups, pressing down lightly to compact them. If desired, sprinkle breadcrumbs on top of each cup and drizzle with melted butter.

Bake:
Bake for 15–20 minutes, or until the tops are golden brown and crispy.

Serve:
Let the Mac & Cheese Cups cool for a few minutes before removing them from the tin. Serve warm — perfect for a snack or appetizer!

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