Photo of French onion soup roasted potatoes by WW

French onion soup roasted potatoes

Total Time
45 min
15 min
30 min
The beloved soup featuring silky onions and gooey cheese is at the heart of this inventive side dish. We blanket simple roasted potato slices with caramelized onions flavored with thyme, then finish the pan with a sprinkle of nutty Gruyere cheese. The secret to quicker caramelized onions is a pinch of baking soda, which changes the pH and breaks down the onions more quickly. Make sure to use no more than the amount called for, as too much will affect the taste and make the onions mushy.


Cooking spray

4 spray(s)

Uncooked Yukon gold potato

1 pound(s), cut crosswise into 1/2-inch-thick slices

Kosher salt

1 tsp, divided

Black pepper

½ tsp, divided

Spanish onion

1½ pound(s), halved lengthwise and cut into ½-inch lengthwise slices (cut pole to pole, not across the equator)

Dried thyme

½ tsp

Baking soda


Gruyère cheese

½ cup(s), shredded, shredded


  1. Preheat the oven to 450°F. Coat a small sheet pan (such as a quarter sheet pan) with cooking spray. Arrange the potato slices on the pan and coat the tops with cooking spray. Sprinkle ½ tsp salt and ¼ tsp black pepper over the potato slices. Roast until browned and tender, about 25 minutes, turning slices over after 15 minutes.
  2. Meanwhile, coat a large nonstick skillet with cooking spray and heat over medium-high. Add the onions to the pan; cover and cook until starting to soften, about 5 minutes, stirring occasionally. Uncover the pan and sprinkle the onions with the remaining ½ tsp salt and ¼ tsp black pepper, the thyme, and baking soda. Reduce the heat to medium, cover the pan, and cook, stirring occasionally, until the onions are tender and deeply browned, 12 to 15 minutes.
  3. Remove the potatoes from the oven and turn the oven to high broil. Arrange the caramelized onions over the potatoes and sprinkle evenly with the cheese. Broil until the cheese melts and begins to brown, 1 to 2 minutes.
  4. Serving size: one-fourth of the potatoes