Cauliflower gratin

I was craving mac and cheese last night, but had no mac. I did, however have a behemoth head of cauliflower. This is what I came up with. It definitely satisfied the craving. We had it with corn and baked chicken tenders served over wild rice. Yum!
Cauliflower Gratin
Makes 6-8 side servings
Ingredients:
1 large head cauliflower, washed and broken into florets
2 tb butter
2 tb flour
1/8 tsp dried thyme
2 tbsp minced garlic
1 1/2 cup milk
2 1/2 cups grated cheese (I used a combo of sharp cheddar and mozzarella)
1/4 cup sour cream
1/4 cup panko breadcrumbs (I'm trying to use a box up, can you tell?)
1 tbsp olive oil
1 tsp garlic powder
salt and pepper to taste

Directions:
Preheat oven to 400. Steam cauliflower until crisp tender. In a large sauce pot (large enough to fit the head of cauliflower), melt butter and stir in flour over medium heat. Add garlic and thyme and cook a minute. Slowly add milk (1/4 cup at a time), stirring constantly. Once all milk is added, increase heat to high and bring to a slow boil. Reduce heat to medium and cook 4 minutes. Reduce heat again to low and add cheese and sour cream. Stir until melted and combined. Salt and pepper to taste.

In a small bowl, combine panko, oil and garlic powder.

Add cauliflower to pot of cheese sauce and gently stir until all cauliflower is coated. Drain off any excess liquid and pour into a 3 qt casserole (broiler safe) dish. Sprinkle with the breadcrumb mixture. Bake at 400 on the middle rack for 20 minutes. Broil on high until the top is crispy and bubbly. I broiled mine from the middle of the oven and it took about 10 minutes. Allow to sit 5 minutes before serving.