Preheat oven to 350°; grease medium baking dish

Dice onion; heat 2 tbsp oil in skillet + cook onion 4-6 min til soft; add one container alfredo, one container creme fraiche + tear up 8 slices cheese; add ½ the cheese to the sauce + simmer 3-4 min, stirring til cheese melts; season with pepper; cover + set aside

Peel 4 potatoes, cut in half + slice into 1/8-inch slices; add to a large pot of salted water + boil; cook 5 min until al dente; drain potatoes + add cheese sauce

Add potatoes to baking dish; layer top with remaining cheese + salt/pep

Cover with greased foil + bake 25-30 min til melty; remove foil + bake 5-10 min til top is golden