1. Prep the Oven and Dish

• Preheat your oven to 350°F (175°C).
• Lightly grease a 9×13-inch baking dish and set aside.

2. Cook the Macaroni

• Bring a large pot of salted water to a boil.
• Cook macaroni until just al dente according to package instructions.
• Drain and set aside.

3. Make the Cheese Sauce

• In a medium saucepan over medium heat, melt 1/4 cup butter.
• Stir in flour and mustard powder, whisking constantly to form a smooth roux. Cook for 1–2 minutes until slightly golden.
• Slowly whisk in milk, continuing to stir until the sauce thickens (about 5 minutes).
• Remove from heat and stir in 3 cups of cheddar cheese, salt, and pepper. Mix until smooth and creamy.

4. Combine Pasta and Sauce

• Add the cooked macaroni to the cheese sauce and stir to coat evenly.

5. Assemble the Casserole

• Pour the mac and cheese mixture into the prepared baking dish.
• In a small bowl, mix panko breadcrumbs with melted butter.
• Sprinkle the buttery crumbs and the remaining 1 cup of cheddar cheese over the top.

6. Bake and Serve

• Bake for 25–30 minutes or until the top is golden brown and bubbly.
• Let rest for a few minutes before serving.