Potatoes and Sour Cream Gratin

I wanted to make scalloped potatoes to go with the Pecan-Crusted Chicken Tenders, however, I didn't feel like making a béchamel sauce and I was out of cream (shocking, I know). So this was my improvisation. The sour cream separated a bit, but the taste was good. It reminded me of mashed potatoes with buttermilk.

Potatoes and Sour Cream Gratin
4 Yukon Gold potatoes, cut into thin slices (There's no need to peel these because the skin is very thin.)
1/4 onion, cut into thin slices
Salt and pepper
Sour cream
1 (8-oz.) block Cheddar cheese, shredded

1. Place one layer of potato slices in bottom of a lightly greased baking dish. Top with some of the onion slices; sprinkle with salt and pepper. Spread half of sour cream over top; top with half of cheese. Repeat layers once. Sprinkle panko on top of cheese.
2. Bake at 400° for 45 minutes or until potatoes are tender.