with foil.
The foil helps trap steam, which is essential for softening the potatoes.
If your potato slices are slightly thicker or the potatoes seem especially dry and starchy, you can add a few spoonfuls of water before covering the dish.
Do not add a large amount, because the goal is to create steam rather than turn the casserole into soup.
Step 10: Bake Covered
Bake the covered casserole for approximately 1 hour.
During this stage, the potatoes soften and the onion cooks down between the layers.
Step 11: Remove
