Add twice as much broccoli as pasta and you may expect an uprising. But thanks to melty cheddar goodness, your fam will gobble up every bite.
Preheat oven to 350°F. Butter a 10-in. square baking dish. Bring a large pot of salted water to a boil.
Add pasta to boiling water and cook according to package directions until al dente, adding broccoli for last 1 minute of cook time. Drain pasta and broccoli in a colander; return to pot.
While pasta cooks, melt butter in a medium saucepan over medium heat. Whisk in flour to make a thin paste. Continue to cook, whisking constantly, until paste darkens in color and smells nutty, about 3 minutes. Gradually add milk, whisking to incorporate. Raise heat to medium-high, and cook, stirring often to prevent scorching, until sauce thickens, 3 to 5 minutes. Stir in paprika, mustard, salt, and pepper.
Add 1 1/2 cups of the cheese to pasta-broccoli mixture. Fold in sauce, stirring gently to coat. Transfer mixture to prepared baking dish, and top with remaining 1/2 cup cheese. Bake uncovered until cheese fully melts and mixture bubbles around edges, about 30 minutes. Let stand 10 minutes before serving.