Ingredients
Equipment
Method
For the Caramelized Onions
- Choose your onions, preferably yellow or sweet like Vidalias, and slice them thinly and uniformly, about 1/8-inch thick. Consistency in slicing ensures they cook at the same rate.
- In a large, heavy-bottomed pan or Dutch oven, melt 2 tablespoons of butter with 1 tablespoon of olive oil over medium-low heat.
- Add all your sliced onions to the pan. It might look like a mountain, but they will cook down significantly. Stir to coat them evenly in the fat.
- Reduce the heat to low. Cook the onions slowly, stirring frequently (every 5-10 minutes), for at least 30-45 minutes, or even longer, until they first soften, then turn translucent, and gradually start to take on a golden hue.
- Keep cooking, allowing them to deepen in color to a rich, dark golden brown. They should be incredibly tender and sweet. If dark bits stick to the bottom, you can add 1-2 tablespoons of water, vegetable broth, or dry white wine to deglaze.
- Once they're a deep golden brown and wonderfully soft, season lightly with salt and pepper. Set aside to cool.
Prepare for Baking
- Preheat your oven to 375°F (190°C). Generously butter a 13-by-9-inch baking dish, ensuring every surface is coated for easy release and a golden crust.
- In a small bowl, stir together the sour cream and onion soup mix. Refrigerate it while you prepare the potatoes so the flavors have time to meld.
Cook the Potatoes
- Place the peeled and chunked russet potatoes into a large pot and cover them with cold water by 1 inch. Bring the water to a boil over high heat and cook until the potatoes are completely fork tender, usually 20 to 25 minutes.
- Drain the potatoes very well, shaking off excess water, and return them to the same pot. Place the pot back on the same burner (heat turned off) for a minute or two to allow any remaining moisture to evaporate. Mash them until there are no visible lumps, using a potato ricer or masher for a fluffy result.
Assemble the Casserole Base
- Add the prepared sour cream and onion dip mixture, melted salted butter, warmed heavy cream, cooked and crumbled bacon, shredded Monterey Jack cheese, 1/2 cup of the crispy fried onions, and 1 1/2 teaspoons of kosher salt to the mashed potatoes. Stir gently to combine everything, being careful not to overmix, which can lead to a gummy texture.
- Season to taste with black pepper. Taste and adjust the seasoning; potatoes absorb a lot of salt!
Layer and Top
- Spread your prepared (and cooled) caramelized onions evenly on the bottom of the buttered baking dish. This foundational layer is key to the deep, complex flavor of the casserole.
- Transfer the mashed potato mixture to the prepared baking dish, spreading them evenly over the caramelized onions.
- For the topping: In a small bowl, stir together the remaining 1 cup of crispy fried onions, the lightly crushed kettle cooked potato chips with sea salt, and the grated Parmesan cheese. Sprinkle this mixture evenly over the top of the mashed potatoes.
Bake and Serve
- Bake in the preheated 375°F (190°C) oven until the casserole is bubbling around the edges and the topping is beautifully browned and crisp, typically 15 to 20 minutes.
- Remove from the oven and let it rest for a few minutes before serving. Just before serving, sprinkle with fresh chopped chives or green onions for a burst of color and fresh flavor.
Notes
This Mashed Potato Casserole is a perfect make-ahead dish, with components like caramelized onions and bacon able to be prepared days in advance. Ensure to warm your heavy cream for the creamiest mashed potatoes and avoid overmixing to prevent a gummy texture. The crispy topping adds an essential textural contrast. Nutrition information is estimated based on common ingredients and serving sizes and may vary.