Mix together potatoes, eggs, and milk in a large bowl.

Stir flour, Parmesan cheese, Cheddar cheese, bacon bits, onion salt, baking powder, salt, and black pepper into potato mixture using a fork.

Heat corn oil and butter in a large skillet over medium heat.

Spoon about 2 tablespoons potato mixture into per patty into skillet. Cook patties until golden brown, about 4 minutes per side.

Drain cooked pancakes on paper towel-lined plate.