Equipment Needed
- Mandoline slicer or very sharp knife and steady hand
- 9×13 inch baking dish
- Large saucepan or Dutch oven
- Whisk
- Mixing bowls
- Box grater
Step-by-Step Instructions
My journey always begins with the potatoes. Peeling and slicing them thinly and uniformly is the most important step for even cooking. I use a mandoline slicer set to 1/8-inch thickness—it’s a game-changer for speed and consistency. If you’re using a knife, take your time. I place all the slices in a large bowl of cold water as I work to prevent browning. Once sliced, I drain them and pat them very dry with clean kitchen towels. I learned the hard way that wet potatoes will steam instead of bake in the sauce, leading to a watery casserole. Dry potatoes are non-negotiable for a creamy result.
Next, I build the luxurious cheese sauce, which is the soul of the dish. In my large saucepan, I melt the butter over medium heat. I add the diced onion and cook until soft and translucent, about 5 minutes, then stir in the minced garlic for just 30 seconds until fragrant. I sprinkle the flour over the onion-butter mixture and whisk constantly for a full two minutes to cook out the raw flour taste. This is my roux, and it must smell nutty. Then, I slowly whisk in the milk and heavy cream, a little at a time at first, until the mixture is smooth. I continue to whisk as it comes to a gentle simmer and thickens beautifully, about 5-7 minutes.
Now, for the magic. I turn the heat to low and stir in 2 cups of the freshly shredded sharp cheddar cheese, one handful at a time, letting each melt completely before adding the next. This patience ensures a silky, lump-free sauce. Once the cheese is melted in, I remove the saucepan from the heat and whisk in the salt, pepper, paprika, and that crucial pinch of nutmeg. The sauce should coat the back of a spoon thickly. I give it a taste—it should be gloriously cheesy and well-seasoned.(See the next page below to continue…)