Fennel and Sweet Potato Gratin

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This potato gratin honestly took some trial and error to get right. My first attempt involved caramelizing the onions and fennel before mixing them with the cream, but after an hour and a half in the oven, they’d cooked down too much and practically disappeared. The second version skipped that step and let everything caramelize together in the oven instead. Much better.

I also tested peeling versus not peeling the potatoes. Turns out, leaving the skins on works fine and saves time. Between slicing everything thin on a mandoline and arranging the layers, there’s already enough work involved. No point adding unnecessary steps.

About that mandoline: use the guard and go slow, especially when you get near the end of each potato. The blades are sharp and will bite if you’re distracted or rushing. A cut-resistant glove is worth considering if you’re new to using one. If you have knife skills precise enough to get paper-thin, even slices, go for it, but the mandoline makes this much easier. Uniform thickness matters here so everything cooks at the same rate.

The finished gratin is absolutely worth the effort. The potatoes turn tender and luscious, with crispy edges on top. Red, white, and sweet potatoes together taste wintery without being too sweet. The onions and fennel mellow as they cook, going from sharp to caramelized and slightly sweet. Gruyère and Parmesan obviously adds decadent cheesiness. This works as a side for any cold-weather meal that needs something substantial on the plate.

Step by Step Guide to Making Fennel and Sweet Potato Gratin

  1. Prep Oven and Cheeses:

    • Preheat oven to 400°F. Mix comte and parmesan cheeses, setting aside 1/3 for topping. In the larger cheese portion, mix in cream, salt, pepper, garlic, sage, and thyme.

  2. Slice Vegetables:

    • Slice potatoes, fennel, and onions using a mandoline for even thickness. Combine in a large bowl.

  3. Combine with Cream Mixture:

    • Toss vegetables with cream and cheese mixture, ensuring each slice is coated.

  4. Prepare Baking Dish:

    • Butter a large casserole dish or 12″ cast iron skillet. Neatly stack potato, onion, and fennel slices in the dish vertically.

  5. Bake:

    • Cover and bake for 30 minutes. Uncover and bake for another 30 minutes. Sprinkle with reserved cheese and bake until golden brown, about 30 minutes more.

  6. Rest and Serve:

    • Let the gratin rest for at least 15 minutes before serving.

NOTES

  • Cheese Choice: The nutty flavor of Comte or Gruyere adds depth.
  • Mandoline Use: Ensure uniform thickness for even cooking.
  • Seasoning: Don’t shy away from the salt; it’s crucial for flavoring this hearty dish.
  • Resting Time: Allows the gratin to set and flavors to meld.

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Fennel and Sweet Potato Gratin

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  • Author:     Tux Loerzel


  • Total Time:     2 hours


  • Yield:     6–8 servings 1x


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Description

Who could say no to tender, delicate, richly flavored potatoes with crunchy, crispy top edges? The mix of red, white, and sweet potatoes is wonderfully wintery without being too sweet, and the onions and fennel caramelize in the oven and their flavors go from pungent and intense to rich, mellow, and slightly sweet. The mix of cheeses adds a salty, nutty richness, and the sage, thyme, and garlic make this dish the perfect side to any winter meal.

Ingredients

  • 1 cup, grated (alternatives: Gruyere or Emmental) Comte Cheese
  • ½ cup, grated Parmesan Cheese:
  • 2 cups heavy cream:
  • 1 tablespoon Kosher salt
  • 1 ½ teaspoons, ground Black Pepper
  • 4 cloves, minced or crushed garlic
  • 1 ½ tablespoons, finely chopped fresh sage
  • 2 teaspoons, finely chopped fresh thyme
  • 1 lb red potatoes
  • 1 lb white potatoes
  • 1 ½ lbs sweet potatoes
  • 1 large or 2 small (about ½ to ¾ lb) fennel bulbs
  • 2 small to medium (about ½ lb) onions
  • 2 tablespoons, softened butter

Instructions

  1. Prep Oven and Cheeses:
    • Preheat oven to 400°F. Mix comte and parmesan cheeses, setting aside 1/3 for topping. In the larger cheese portion, mix in cream, salt, pepper, garlic, sage, and thyme.
  2. Slice Vegetables:
    • Slice potatoes, fennel, and onions using a mandoline for even thickness. Combine in a large bowl.
  3. Combine with Cream Mixture:
    • Toss vegetables with cream and cheese mixture, ensuring each slice is coated.
  4. Prepare Baking Dish:
    • Butter a large casserole dish or 12″ cast iron skillet. Neatly stack potato, onion, and fennel slices in the dish vertically.
  5. Bake:
    • Cover and bake for 30 minutes. Uncover and bake for another 30 minutes. Sprinkle with reserved cheese and bake until golden brown, about 30 minutes more.
  6. Rest and Serve:
    • Let the gratin rest for at least 15 minutes before serving.

Notes

Cheese Choice: The nutty flavor of Comte or Gruyere adds depth.

Mandoline Use: Ensure uniform thickness for even cooking.

Seasoning: Don’t shy away from the salt; it’s crucial for flavoring this hearty dish.

Resting Time: Allows the gratin to set and flavors to meld.

  • Prep Time: 30 mins
  • Cook Time: 90 mins
  • Category: Side Dish
  • Method: Oven Baking
  • Cuisine: American

Nutrition

  • Serving Size: 1 slice
  • Calories: 420

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If you liked this, you are going to love these favorite potato gratin recipes:

Tartiflette au Reblochon: The French Alpine Potato Gratin

Italian Béchamel Potato Gratin

Thyme, Pumpkin, and Potato Gratin

Provolone Potatoes au Gratin

Raclette Potatoes au Gratin

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