Step 1

Preheat the oven to 350 F. Grease a 9- by 13-inch baking dish with unsalted butter.

Step 2

Bring a large pot of water to boil. Add the macaroni and cook until al dente, about 7 minutes. Strain in a colander, run cold water over the noodles then set aside.

Step 3

In the same pot the pasta was cooked in, melt the butter over medium heat, add the flour and whisk until smooth. Slowly add the milk while whisking then the heavy cream and bring to a simmer. Stir in the shredded cheese (reserving 1/2 cup for the top) and cream cheese until melted, then season with salt, pepper and granulated garlic powder. Remove the cheese sauce from the heat and stir in the macaroni. Taste and season with salt and pepper.

Step 4

In a separate bowl, whisk the egg together with the sour cream then fold into the macaroni and cheese. Spread mixture into prepared baking dish, fold in the cheese cubes and top with the remaining shredded cheddar cheese.

Step 5

Bake for 20 minutes uncovered or until the top starts to turn slightly golden-brown. Loosely cover with foil and bake for additional 10-15 minutes.