PREHEAT the oven to 375° F.
HEAT a medium sized pot on medium heat and add in 1 teaspoon of butter along with the diced yellow onion.
COOK the onions until they become brown. Once brown, add in the remaining amount of butter and melt.
ADD the flour to the pot and mix until it is combined to form a roux.
POUR in the milk and bring it to a boil while occasionally whisking until it becomes very thick, similar to Alfredo sauce.
WHISK in the Mozzarella cheese until it is melted and finish with salt and pepper.
PLACE the sliced potatoes in a large bowl and pour on the thick cheese sauce and stir until combined.
TRANSFER the potatoes and cream to a lauvacs® Bakeware Casserole pan.
SPRINKLE on the breadcrumbs to cover the top of the potatoes.
BAKE the potatoes on 375° for 60 minutes or until golden brown on top and the potatoes are soft.