In a large bowl, toss the sliced potatoes and onions with the remaining vegetable oil and the kosher salt until everything is lightly coated and the salt is evenly distributed. This helps the vegetables release moisture and start to break down as they bake.
Layer the potato and onion mixture into the prepared casserole dish, piling it in loosely rather than packing it down. You want some air pockets so the edges can crisp and the top can deeply brown. Scatter the butter pieces evenly over the top and gently tuck a few down into the layers.
Cover the dish tightly with foil and place it on the middle rack of the oven. Bake covered for 1 1/2 hours, until the potatoes are very tender and the onions are soft and translucent. During this time, the vegetables will release liquid and start to stew in their own juices and the butter.
Carefully remove the foil (watch for steam) and increase the oven temperature to 375°F (190°C). Return the uncovered dish to the oven and continue baking for 45–60 minutes, or until the top is deeply caramelized, the edges are golden and bubbling, and you can see rendered butter and vegetable juices sizzling around the sides.
Once the top is richly browned and the edges look almost sticky and crisp, remove the casserole from the oven. Let it rest at least 15–20 minutes before serving. This rest time helps the mass settle and firm up slightly so you can scoop out big, cohesive spoonfuls instead of a loose pile.
Taste a small bite and sprinkle with a pinch more salt if needed. Serve warm, spooned straight from the glass casserole dish, with all the deeply caramelized bits and buttery juices scooped over each portion.
Variations & Tips
To make this feel more like a complete main dish for Easter or other family gatherings, you can tuck in thinly sliced smoked sausage or leftover ham between the potato layers while still keeping the ingredient list simple. If you want a slightly creamier version without adding more ingredients, use Yukon Gold potatoes, which naturally break down into a softer, almost gratin-like texture. For extra color and sweetness, swap one of the onions for a thinly sliced sweet onion, or use a mix of yellow and red onions. If you prefer a crisper top, leave the dish in the oven uncovered for an extra 10–15 minutes at the end, watching closely so it doesn’t burn. You can also bake this the day before a big gathering: fully cook it, let it cool, then reheat covered at 325°F until hot and bubbling, uncovering for the last 10 minutes to re-crisp the top. A sprinkle of black pepper or dried thyme over the top before baking adds a little more flavor without complicating the ingredient list too much.
Pages: 1 2
