Cauliflower, Pasta, and Cheese Gratin

Cauliflower, Pasta, and Cheese Gratin(Adapted from CL)

8 cups water
1 1/2 pounds cauliflower florets
3/4 teaspoon salt, divided
8 ounces uncooked tricolor radiatore
1/4 cup all-purpose flour
3 cups milk
2 teaspoons chopped fresh thyme
3 garlic cloves, crushed
4 ounces sharp white cheddar cheese
2 ounces grated fresh Parmesan cheese
3/4 cup finely chopped green onions
2 teaspoons Dijon mustard
1/4 teaspoon black pepper
3/4 cup panko breadcrumbs
2 teaspoons butter, melted

Preheat oven to 400

In a large dutch oven, bring water to a boil and add cauliflower and 1/2 teaspoon salt to boiling water. Cook 4 minutes or until tender. Remove cauliflower with a slotted spoon, reserving cooking liquid, and set cauliflower aside. Bring cooking liquid to a rolling boil. Add pasta, and cook 6-7 minutes or until al dente. Drain pasta.

In a medium sauce pan, whisk together flour and milk in a saucepan. Stir in thyme and garlic. Cook over medium heat until thick - 8 minutes or so - stirring constantly. Remove from heat and stir in 1/4 teaspoon salt, cheeses, onions, mustard, and pepper.

In a large bowl, stir to combine cauliflower, pasta, and cheese sauce in a large bowl. Spoon the cauliflower mixture into a 13X9" baking dish. Combine panko breadcrumbs with butter and sprinkle evenly over cauliflower mixture. Bake 20 minutes or until lightly browned.