Step 1: Bring a large pot of salted water to a boil. Cook the elbow macaroni one minute less than the package directions. Drain (don't rinse) and set aside.
Step 2: In the same pot over medium heat, melt butter. Whisk in flour and cook for 1-2 minutes until light golden and nutty.
Step 3: Slowly pour in milk, about 1/2 cup at a time, whisking continuously. Cook over medium heat, stirring frequently, until sauce thickens (about 5-7 minutes).
Step 4: Remove from heat. Stir in Dijon mustard, smoked paprika, garlic powder, and onion powder. Add cheddar, Monterey Jack, and Parmesan one handful at a time, stirring until melted. Season with salt and pepper.
Step 5: Add cooked pasta to cheese sauce and fold until every piece is coated. Transfer to an oven-safe baking dish.
Step 6: In a small bowl, combine panko breadcrumbs, melted butter, and minced garlic. Sprinkle evenly over the mac and cheese.
Step 7: Broil on high for 2-3 minutes, watching carefully, until breadcrumbs are golden brown. Top with bacon, green onions, hot sauce, or jalapeños and serve immediately.
