[blessedx7]

1/2 stick butter
1 small onion, very finely chopped
1/4 c all purpose flour
2c milk
1tsp salt
1/2 tsp black pepper
1c sour cream
6c peeled and diced russet potatoes
2c peeled and diced sweet potato
2c cubed fully cooked ham
1c shredded Cheddar cheese, divided
1/4 c chopped green onions

1. Preheat oven to 375. Coat a 9x13in casserole dish with nonstick cooking spray.
2. Melt butter in a large heavy skillet over med heat. Add onion, cook until onion begins to soften, stirring occasionally. Whisk in flour until onion is evenly coated. Add mlk, salt, and pepper, stirring occasionally until mixture simmers and begins to thicken. Add sour cream; stir to combine.
3. In a large bowl, combine potatoes, ham, 1/2c cheese, and green onions. Spread potato mixture into prepared dish. Pour white sauce over potato mixture. Sprinkle with remaining 1/2 c cheese. Bake until bubbly and potatoes are fork tender, 50-60min. Let stand 5 min before serving.

(This is even better heated up as leftovers so we always make extra!)