Preheat the oven to 350 degrees F. Grease a 9- by 13-inch baking dish with butter.
Bring a large pot of salted water to a boil, add the macaroni and cook, stirring occasionally, until al dente, about 7 minutes. Strain in a colander, run cold water over the pasta and set aside.
Using the same pot the macaroni was cooked in, melt the 1/4 cup butter over medium heat, add the flour and whisk until smooth. While whisking constantly, slowly add the milk and then the cream. Bring to a simmer, add the cream cheese and the shredded Cheddar except for 1/2 cup and stir until melted. Stir in the granulated garlic, 1/2 teaspoon salt and 1/4 teaspoon pepper. Remove the cheese sauce from the heat and stir in the macaroni. Season with salt and pepper.
Whisk together the eggs and sour cream in a small bowl and then fold into the macaroni and cheese. Spread the mixture into the prepared baking dish, fold in the cubed Cheddar and top with the reserved 1/2 cup shredded Cheddar. Bake until the top just begins to brown, about 20 minutes. Loosely cover with foil and bake 10 to 15 minutes more.