Preheat Oven:

Set oven to 350°F (175°C) and grease a 9x13-inch casserole dish.

Cook Pasta:

Boil the pasta in salted water until just al dente. Drain and set aside.

Make the Sauce:

In a saucepan over medium heat, melt the butter. Stir in the flour and cook for 1 minute, whisking constantly. Gradually add the milk, continuing to whisk until the mixture thickens—about 3–5 minutes.

Add Cheese & Cream:

Stir in sour cream, 1 cup of the cheddar, garlic powder, salt, and pepper. Stir until melted and smooth.

Combine Ingredients:

In a large bowl, mix together the cooked pasta, chopped ham, peas (if using), and the cheese sauce. Transfer to the prepared casserole dish.

Add Topping:

Sprinkle remaining 1/2 cup cheese on top. In a small bowl, mix the crushed crackers with melted butter and sprinkle over the cheese.

Bake:

Bake for 30–35 minutes, or until bubbly and golden on top. Let cool for 5–10 minutes before serving.