Preheat your oven to 375°F. This ensures your Baked Mac and Cheese will bake evenly and get that perfect golden color.
In a large pot, bring salted water to a boil and add the dry elbow macaroni. Cook it according to package directions until it’s al dente. You want it firm because it will continue cooking in the oven.
Once cooked, drain the pasta and rinse it under cold water to stop the cooking process. This will also help prevent it from sticking together.
In a large oven-safe skillet, melt 5 tablespoons of unsalted butter over medium heat. Once melted, add the minced onion with a sprinkle of salt. Sauté for about two minutes until the onions are soft and fragrant.
Add in the minced garlic and stir for another minute, until it becomes aromatic but not burnt.
Sprinkle in the all-purpose flour, stirring until the mixture is pasty. This will be the base for our cheese sauce.
Gradually pour in the whole milk while whisking constantly. Keep whisking over low-medium heat until the mixture thickens. You want it to coat the back of a spoon.
Remove the skillet from the heat and whisk in the sour cream until fully incorporated. This adds creaminess.
Now it’s time to combine the cheeses! Add the sharp cheddar cheese and Swiss cheese to the skillet, reserving two cups for later. Stir until melted and smooth.
Gently fold in the cooked pasta, ensuring it’s fully coated in that cheesy goodness.
Transfer the cheesy pasta mixture to a 9×13-inch baking pan. Spread it out evenly to ensure even baking.
In a small saucepan or skillet, melt the remaining 3 tablespoons of unsalted butter over medium heat. Add the Panko breadcrumbs, kosher salt, and garlic powder, stirring until well combined.
Top the macaroni with the reserved cheese and the buttery breadcrumbs. This will create a delicious crunchy topping.
Finally, bake your Baked Mac and Cheese in the preheated oven for about 15 minutes. You want it to be bubbly and golden brown on top.
Once done, remove it from the oven and let it cool for a few minutes. If desired, sprinkle with chopped fresh parsley for a burst of color.