• Peel the potatoes and place them in a bowl of cold water to prevent browning.
• Melt the butter in a large pot over medium-low heat. Add thinly sliced garlic and let it cook until it becomes clear and perfumes the butter.
• While the garlic is cooking, peel and thinly slice the onion. Add it to the pot along with the salt and cook until the onions become soft and clear.
• Slice the potatoes into approximately ¼ inch or ⅓ cm thick slices while the onions are cooking. Do not place the potato slices back into the water. We don't want to wash any potato starch.
• Once the onions are soft, pour in the cream and milk and bring the mixture to a rolling boil.
• Add all the sliced potatoes to the pot and stir so that every slice is coated. Cook for 10-15 minutes until the potatoes are al dente.
• Avoid stirring too often to keep the potato slices intact.
• Once the potatoes are al dente and the sauce is thick, transfer everything to a casserole pan.
• At this point, you can bake it immediately or refrigerate/freeze it for later.

If Cooking Immediately

• Sprinkle the cheese on top and bake at 200C/400F until bubbling and the cheese is melted and brown, about 20 minutes.

If Refrigerating

• Cover with foil and place in the fridge. When time to cook, top with cheese and bake at 175C/350°F for 40 minutes to an hour until bubbling and the cheese is melted and brown.

If Freezing

• Let it cool a bit, then wrap in foil and place in the freezer. You can bake directly from frozen.
• Place in a 175C/350F oven for about 30 minutes. Take it out, sprinkle it with cheese and place back in the oven until the cheese is melted and brown, about 20 minutes.