2 cups cauliflower florets
2 tablespoons unsalted butter
2 tablespoons all-purpose flour
1 cup half and half, or more, as needed
2 ounces cream cheese
2 teaspoons Dijon mustard
1/2 teaspoon garlic powder
1 1/2 cups shredded sharp cheddar cheese
Kosher salt and freshly ground black pepper, to taste
2 tablespoons chopped fresh chives
Preheat oven to 375 degrees F. In a large pot of boiling salted water, cook pasta according to package instructions. Within the last 3 minutes of cooking time, add cauliflower; drain well. Melt butter in a 9-inch oven-proof skillet over medium high heat. Whisk in flour until lightly browned, about 1 minute. Gradually whisk in half and half, and cook, whisking constantly, until incorporated, about 1-2 minutes. Stir in cream cheese, Dijon and garlic powder until slightly thickened, about 2 minutes. Stir in 1 cup cheese until melted, about 1-2 minutes. If the mixture is too thick, add more half and half as needed; season with salt and pepper, to taste. Stir in pasta and cauliflower; gently toss to combine. Sprinkle with remaining 1/2 cup cheese. Place into oven and bake until bubbly, about 12-15 minutes. Serve immediately, garnished with chives, if desired.