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Fennel and Onion Gratin Potatoes with Gruyère Cheese

  • Author: Krista
  • Prep Time: 15 min
  • Cook Time: 50 min
  • Total Time: 1 hour 5 minutes
  • Yield: 8-10 servings 1x


  • 3 large russet potatoes – washed and thinly sliced
  • 1 large onion – chopped into 1” slices
  • 1 large or two small fennel bulbs – cores removed and bulb chopped to match onions in size
  • fresh thyme – about 5 sprigs
  • 1 clove garlic or 1 TBL chopped garlic from a jar
  • 5 cups whole milk or cream
  • 1+1/2 block of Gruyere cheese shredded
  • salt and pepper to taste
  • olive oil for sauteeing


  1. In a deep pot heat olive oil over medium heat. Add in the chopped fennel and sautee for 5 min. Then add in the onion and garlic. Season with salt and pepper and continue to stir so the garlic doesn’t burn. Sautee until onions are slightly tender.
  2. Add in the milk (or cream), thyme bundle and more salt and pepper, heat for 5 minutes then add in the sliced potatoes. Mix gently until most of the potatoes are covered (as they cook they will settle down into the pot). Continue to cook on a low simmer, stirring occasionally, until potatoes are fork-tender. Fork should slide into potato but not be completely cooked.
    NOTE – taste the milk mixture. You will probably want to add more salt and pepper. If the milk mixture is bland that’s how your potatoes will taste. Potatoes can take a lot of seasoning, don’t be afraid to go a little heavier than you typically would.
  3. While the potatoes are simmering prepare your baking dish. Spray a 9×13 (or similar) dish with non-stick cooking spray.
  4. Pour half the potatoes into the prepared baking dish and sprinkle with a little Gruyere cheese. Top with the rest of the potato mixture then finish with the remaining cheese.
  5. Cover lightly with foil and bake for about 40 minutes. Remove foil and cook another 10 minutes to brown the cheese.


No fennel? No problem, in my original recipe I didn’t add fennel so I can assure you it’s just as good without it.

When I made this for Easter 2020 I didn’t have quite enough Gruyere so I mixed in some Parmesean and it was just as delicious.

If you can’t find Gruyere try looking for Comte’ or Beaufot they are great substitutes. I find Gruyere at Kroger at the Murry’s Cheese shop.

Keywords: Fennel and Onion Gratin Potatoes with Gruyère Cheese