Before You Begin:
Prepare your cookware as needed. Cooking times and results may vary depending on your equipment and ingredients.
Preheat the oven to 375°F (190°C).
Bring a pot of salted water to a gentle boil. Cook tortellini according to package directions until just tender. Add broccoli during the last 1–2 minutes. Drain well.
In a skillet over medium heat, melt butter. Whisk in flour and cook 1–2 minutes until smooth.
Slowly whisk in milk, stirring constantly, and cook 4–5 minutes until slightly thickened.
Remove from heat and stir in Parmesan, garlic powder, nutmeg (if using), salt, and pepper.
Gently combine tortellini and broccoli with the sauce. Transfer to a lightly greased baking dish.
Sprinkle mozzarella over the top. Add breadcrumb topping if using.
Bake for 20–25 minutes, or until the top is lightly golden and the edges are bubbling.
Let rest for 5 minutes before serving.