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Creamy Cheesy Onion Mashed Potato Casserole

creamy cheesy onion mashed potato casserole - featured image
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A rich and comforting casserole featuring creamy mashed potatoes, caramelized onions, and a blend of sharp cheddar and Monterey Jack cheese, perfect for holidays or weeknight dinners.

Ingredients

Scale
  • 4 cups (about 1 kg or 2.2 lbs) well-seasoned mashed potatoes, preferably homemade or store-bought (avoid instant for best texture)
  • 2 medium yellow onions, thinly sliced
  • 4 tablespoons (60 g or 0.25 cup) unsalted butter
  • 1/2 cup (120 ml or 4 fl oz) sour cream (can substitute Greek yogurt)
  • 1 1/2 cups (150 g or about 6 oz) shredded cheese (blend of sharp cheddar and Monterey Jack recommended)
  • 1 teaspoon garlic powder
  • Salt and black pepper to taste
  • Chopped fresh chives or green onions (optional, for garnish)

Instructions

  1. Caramelize the onions: Heat 2 tablespoons (30 g) of unsalted butter in a large skillet over medium-low heat. Add the thinly sliced onions and a pinch of salt. Cook slowly, stirring frequently, until onions are deep golden brown and sweetly fragrant, about 15-20 minutes.
  2. Prepare the mashed potato mixture: In a large mixing bowl, combine 4 cups (about 1 kg) mashed potatoes with 1/2 cup (120 ml) sour cream, 1 teaspoon garlic powder, salt, and pepper to taste. Stir until smooth and creamy. Add a splash of milk or cream if needed to loosen the mixture.
  3. Mix in caramelized onions and cheese: Fold the caramelized onions into the mashed potatoes gently. Reserve about 1/2 cup (50 g) shredded cheese for topping, and mix the remaining 1 cup (100 g) cheese evenly into the potato mixture.
  4. Assemble the casserole: Lightly butter a 9×13-inch (23×33 cm) baking dish. Spread the potato and onion mixture evenly into the dish and smooth the top. Sprinkle the reserved shredded cheese evenly over the surface.
  5. Bake: Preheat oven to 375°F (190°C). Bake the casserole for 20-25 minutes until the cheese topping is melted, bubbly, and golden brown.
  6. Garnish and serve: Remove from oven and let rest for 5 minutes. Sprinkle chopped fresh chives or green onions on top. Serve warm.

Notes

Caramelizing onions low and slow is key to avoid bitterness and achieve sweetness. Use unsalted butter to control salt levels. Avoid over-stirring the potatoes to keep a fluffy texture. If cheese browns too quickly, cover casserole loosely with foil halfway through baking. Homemade mashed potatoes yield best texture but quality store-bought works well. Adjust seasoning before baking.

Nutrition

Keywords: mashed potato casserole, cheesy mashed potatoes, caramelized onions, holiday side dish, comfort food, easy casserole

Find it online: https://swooshspice.com/creamy-cheesy-onion-mashed-potato-casserole-recipe-easy-and-perfect-for-holidays/