scalloped potatoes

So, I wanted scalloped potatoes today. Something cheesy, creamy, and delicious. I didn't find a recipe that fit exactly what I wanted. So I combined a few of them with my mom's mac-n-cheese recipe. Yeah, sounds good right? Here it is:

Yield: 3-4 servings
Prep time: 20 minutes
Cook time: 1 hour

2 baked potatoes, skinned and thinly sliced
2 tbs butter or margarine
1/4 c diced onion
2 tsp. flour
1/4 tsp. ground mustard
3/4 c skim milk
1 1/2 c low fat cheddar cheese
1/2 c low fat mozzarella cheese
salt and pepper

Preheat oven to 350*
1. Slice potatoes and bring to a boil in a pot of water
2. In a sauce pan, melt butter in pan, add onions and stir
3. Add ground mustard, salt and pepper, stir
4. Add flour and stir. This mixture should now be paste like.
5. Add milk slowly, stirring in. Let warm.
6. Drain potatoes and spray the inside of a 6x8 glass pan
7. Layer pan: potatoes, cheddar cheese and mozzarella cheese, potatoes, cheddar cheese and mozzarella, cheese. Pour milk mixture over the top.
8. Cover with aluminium foil and cook for 45 minutes
9. Remove foil, top with extra cheese and cook for an extra 10 minutes
10. Cool and enjoy