This creamy potato bake is perfect for colder weather. It goes perfectly with roasts, chicken, braised meats, and even turkey! Although the steps to making this gratin are very simple, it involves a lot of patience. This dish bakes to at least an hour, and needs to rest 30-45 minutes before consumption. This actually makes this dish perfect for dinner parties since it has a resting time.
Since the sauce is milk based as opposed to just heavy cream, it will seem like it is overly liquidy - but don't worry, those potatoes will soak it all up throughout the cooking process and cooling period. The thickness of your potato slices and how many layers of potatoes you use will also impact the cooking time. You will need to check on it and use a fork or sharp knife to judge whether or not it is ready.
I typically like using russet potatoes but golden potatoes work just fine. For a richer consistency, you can swap a portion of the milk with heavy cream or half and half.
3 tbsp butter
2.5 tbsp flour
1 head of garlic (6-8 cloves)
2 cups whole milk
3/4 cup heavy cream
Salt and pepper to taste
2 cups shredded cheddar
1/2 cup grated parmesan cheese (optional)
4 Russet potatoes
3 small shallots or 1 small yellow onion, thinly sliced
Over medium low heat, melt the butter, then add the flour and mix consistently to make a roux. The roux should be thick, like a paste.
Add the cold milk and heavy cream as you whisk constantly until there are no lumps.
Add crushed garlic, freshly ground black pepper, and salt. Bring to a simmer over low heat until the sauce thickens. Shred the cheese while you wait.
Set the sauce aside and dump in all the shredded cheddar cheese. Mix in to melt.
Peel the potatoes then slice into ¼ inch slices. You can also use a mandolin to get nice thin uniform slices. Length wise or rounds works fine.
Assemble the gratin layers in a deep baking dish. For thicker slices, I aim for 3 total layers of potatoes. For thin mandolin-cut slices, I go for 4 or 5 layers.
Layer 1: Small about of cream at the bottom of the baking dish
Layer 2: Slightly overlapping potato layers
Layer 3: Scatter very thin slices of shallots, freshly ground salt & pepper, and fresh thyme leaves.
Layer 4: Extra shredded cheese and/or parmesan
Repeat 7 - 10 until the top of your baking dish. Do not be heavy handed with the sauce layers. Press down slightly after each new potato layer. You should end with a layer of potatoes that are then seasoned with salt and pepper.
Bake at 350 F for 90 minutes or until fork tender. Check every 10 minutes after the 60 minute mark. For thicker potato slices, it may take up to 2 hours total. If the top is starting to get browned but the knife still doesn't go through very easily, cover with foil to keep the potatoes from browning too much.
Optional: Add final layer of cheese. Broil until melted and browned.
Rest for 30-45 minutes before serving.