Chef DaSilva’s stuffed Sweet Onion Potato Gratin is one of the signature sides at 1500° and makes a great addition to any family feast.
Peel and thinly slice the potatoes. Bake in a small covered dish with the cream, horseradish and garlic at 325 degrees F for about 25 minutes. Remove the potatoes from the oven. Mix in the cheese until melted and season with salt to taste. Let the mixture cool and then refrigerate.
Place whole, unpeeled onions in a large pot. Add milk, bay leaves, a bit of salt and enough water to cover everything. Bring the mixture to a boil; turn the onions down to a simmer for 10 minutes. Remove onions from the heat and let them cool in the liquid.
When cooled, remove onions from the milk. Peel and core the onion from the bottom, leaving about 1/2-inch of onion all around. Carefully stuff the onions with the potato gratin mixture. Place the cut side down in a baking dish and season the onion on top with some olive oil, salt and pepper.
Bake the onions at 350F for 10 minutes before serving.