1. Boil pasta 4 min. Add broccoli, cook 4-5 min. more.
2. Meanwhile, heat 1 1/2 c. milk in another large pot over med-high heat until just simmering. Whisk the remainding 1/4 c. milk, flour, garlic powder, salt & pepper in a small bowl. Add the flour mixture to the simmering milk, return to a simmer and cook, whisking constantly until the mixture is thickened, 2-3 min. Remove from the heat and whisk in chedder, Parmesan and mustard until the cheese is melted.
3. Drain the pasta and broccoli and add to the cheese sauce. Return to the heat and cook, stirring, over med-low heat, until heated through, about 1 min.