French Onion Potato Bake

Ingredients

For the potato bake:

• 2 pounds Yukon Gold potatoes, thinly sliced (about 1/8 inch)
• 1 large onion, thinly sliced (yellow or sweet onion)
• 2 tablespoons butter
• 1 tablespoon olive oil (optional, helps prevent onions from scorching)
• 2 cloves garlic, minced
• 1 teaspoon fresh thyme leaves or 1/2 teaspoon dried thyme
• 1 cup beef or vegetable broth
• 1 cup heavy cream or half‑and‑half
• 1 teaspoon salt (divided, or to taste)
• 1/2 teaspoon black pepper (divided, or to taste)​

For the cheesy topping:

• 1 1/2–2 cups shredded Gruyère, Swiss, or mozzarella (or a mix)
• 2 tablespoons grated Parmesan (optional, for extra browning)
• Chopped parsley or chives, for garnish​

This combination mirrors many French‑onion‑style potato gratins and boulangère dishes that layer potatoes with onions, stock, cream, and nutty cheese.​

Step‑by‑Step Instructions

1. Prep the potatoes and pan

1. Heat oven to 375°F (190°C). Butter a 9×13‑inch baking dish or a similarly sized casserole.​
2. Scrub and peel the potatoes if you like; Yukon Gold skins are thin, so peeling is optional. Slice them evenly about 1/8 inch thick using a sharp knife or mandoline so they cook at the same rate.​
3. Rinse slices briefly under cold water, then pat dry with a clean towel; this removes excess surface starch and keeps the sauce from becoming gluey.​

2. Caramelize the onions

1. In a large skillet, melt the 2 tablespoons butter with the olive oil over medium heat.
2. Add the sliced onion, 1/2 teaspoon salt, and a pinch of pepper. Cook, stirring often, until the onions soften and turn translucent, about 10 minutes.
3. Reduce heat to medium‑low and continue cooking 15–20 minutes, stirring occasionally, until the onions are deeply golden and caramelized. If they start to scorch, lower the heat or add a splash of water to loosen browned bits.​
4. Stir in the garlic and thyme; cook 1–2 minutes until fragrant. Remove from heat.

Slowly caramelizing the onions concentrates their natural sugars and mimics the flavor base of French onion soup.​

3. Make the creamy broth

1. In a bowl or large measuring cup, whisk together the broth, cream, remaining 1/2 teaspoon salt, and remaining pepper.
2. Taste and adjust seasoning—you want this mixture well seasoned since it will flavor all the potatoes.​

Some recipes rely solely on cream, others on stock; mixing both gives body plus the savory depth associated with French onion soup.​

4. Layer the potatoes and onions

1. Spread about one‑third of the caramelized onions over the bottom of the prepared baking dish.
2. Arrange half the potato slices on top in overlapping layers, like shingles.
3. Spoon another third of the onions over the potatoes.
4. Layer the remaining potatoes, then finish with the last of the onions.​

Layering ensures that every scoop has both creamy potatoes and sweet onion rather than all the onions sitting on top.​

5. Add liquid and bake

1. Slowly pour the broth‑and‑cream mixture evenly over the layered potatoes and onions, tilting the pan slightly to distribute. The liquid should come close to the top but not fully submerge everything.​
2. Cover the dish tightly with foil, tenting it slightly so it doesn’t press onto the potatoes.
3. Bake, covered, for 40–45 minutes, until the potatoes are mostly tender when pierced with a knife.​

Covering the dish during the first stage traps moisture and helps the potatoes cook through before the top browns.​

6. Add cheese and finish baking

1. Remove the foil and sprinkle the shredded Gruyère (or other cheese) evenly over the top. Add Parmesan if using.
2. Return the dish to the oven and bake uncovered 15–20 minutes more, until the cheese is melted, bubbly, and deeply golden in spots and the potatoes are completely tender.​
3. If the top browns too quickly, loosely tent with foil; if it needs extra color, you can broil for 1–2 minutes at the end, watching closely.​
4. Let the bake rest at least 10–15 minutes before serving; this helps the sauce thicken and makes it easier to cut clean portions.
5. Sprinkle with chopped parsley or chives just before serving for freshness and color.
   
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