Easy cheesy scalloped potatoes

Ingredients:
4 medium potatoes (peeled and sliced thin)
1/4 chopped onions
2 tbsp butter
2 tbsp flour
salt, pepper to taste
1/4 cups milk
1/2 cup shredded cheese
1/2 cup parmesan cheese

Directions:
- Preheat over to 350 degrees.
- In a sauce pan, melt butter and cook onions until transparent.
- Add flour, salt and pepper. Mix.
- Add milk. Stir.
- Add cheese. Stir and let boil for a bit until sauce becomes thick.
- Peel and slice potatoes.
- Grease bottom of pyrex dish.
- Layer (2 potatoes) sliced potatoes.
- Pour half of the sauce.
- Add remaining sliced potatoes.
- Top with remaining sauce.
- Sprinkle parmesan cheese on top.
- Cover with aluminum foil and bake for 30 minutes.
- Remove foil and bake for another 30 minutes.
- Let rest for 5 minutes.
- Enjoy.