Step 1

Preheat the oven to 375, and lightly butter an 8x8" oven-safe dish.

Step 2

First, cook the rotini pasta in plenty of salted boiling water until al dente--about 1-2 minutes less than the package directions. Drain and set aside.

Step 3

In a small saucepan, melt the butter over medium heat. Whisk in the flour, and cook for 1 minute until homogenous. Whisk constantly.

Step 4

Next, stream in the milk, 1/4 cup of the cream, salt, pepper, onion powder, and garlic powder. Lower the heat and cook while stirring occasionally until slightly thickened. It will take about 5-8 minutes, and the mixture will coat the back of a spoon when it's properly thicken.

Step 5

In a large bowl, combine the cooked pasta, cream sauce, sour cream, 1 cup of the grated cheddar, ham and the sliced scallions. Stir well to combine.

Step 6

Pour the mixture into the prepared baking dish. Top with the remaining 1/2 cup of grated cheese. Drizzle the remaining 1/4 cup of heavy cream evenly over the mixture.

Step 7

Cover with foil, and bake for 20 minutes. Remove the foil and bake uncovered for 5 minutes to slightly crisp up the cheese on top.

Step 8

Let stand for 5 minutes before scooping and serving.