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Caramelized Onion Mashed Potato Bake
A comforting baked mashed potato casserole loaded with sweet caramelized onions and nutty Gruyere cheese. The combination of warm buttermilk and melted butter creates a rich, creamy base that contrasts beautifully with the savory, jammy onions. It makes a fantastic side dish for holiday gatherings or a cozy weekend dinner. The top bakes into a light golden brown crust, while the inside stays incredibly soft and flavorful.
Ingredients
- 4 lb. russet potatoes, peeled and cut into 2-inch pieces
- 3 tsp. salt, divided
- 1¼ cups buttermilk, warmed
- ½ cup milk, warmed
- ¼ cup butter, melted
- ½ tsp. freshly ground black pepper
- 5 oz. Gruyère cheese, shredded (1¼ cups)
- 1 cup chopped caramelized onions
- 2 Tbsp. chopped fresh parsley
Instructions
- 1Heat the oven to 350°F. Place the peeled and cut potatoes in a large Dutch oven, cover them with water, and add 2 teaspoons of the salt. Bring the pot to a boil over medium-high heat and cook for about 20 minutes until the potatoes are tender, then drain the water.
- 2Put the drained potatoes back into the Dutch oven and turn the heat down to low. Cook them for 3 to 5 minutes, stirring occasionally, until the potatoes are completely dry.
- 3Crush the dried potatoes with a potato masher until they reach your preferred texture. Pour in the warm buttermilk, warm milk, melted butter, black pepper, and the remaining 1 teaspoon of salt, mixing gently just until everything is combined.
- 4Fold the shredded Gruyere cheese, chopped caramelized onions, and fresh parsley into the potato mixture. Transfer the blend into a lightly greased 2.5-quart baking dish or divide it evenly among eight 10-ounce ramekins.
- 5Place the dish in the preheated oven and bake for about 35 minutes until the top develops a light golden brown color.