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Leek, Carrot, and Potato Au Gratin Recipe

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4.3 from 4 reviews

This Leek, Carrot, and Potato au Gratin is a comforting, creamy baked dish featuring layers of tender potatoes, sweet carrots, and sautéed leeks, all smothered in a flavorful cheese sauce infused with herbs. Perfect as a hearty side or a vegetarian main, this classic gratin recipe offers a rich, cheesy experience with a lightly crisped top.

Ingredients

Vegetables

  • 3 medium leeks, thinly sliced
  • 2 large carrots, thinly sliced (1/8 inch)
  • 3 large red or white potatoes (1 lb), thinly sliced (1/8 inch)
  • 2 cloves garlic, minced
  • 1 Tbsp fresh chopped chives or parsley to garnish

Cream Sauce

  • 3 Tbsp butter, divided
  • 2 Tbsp all purpose flour
  • 1 1/2 cups whole milk
  • 1/2 tsp salt
  • 1/4 tsp black pepper
  • 1/4 tsp dry mustard powder
  • 2 sprigs fresh thyme (or 1/2 tsp dried thyme)

Cheese

  • 1 1/2 cups shredded melting cheese (cheddar, gruyere, Swiss, Fontina, or mozzarella)

Instructions

  1. Preheat Oven and Prepare Dish: Preheat your oven to 375°F (190°C) and generously grease or butter a 2 1/2 quart (approximately 2.5 liters) baking dish to prevent sticking and ensure easy cleanup.
  2. Sauté Leeks: In a medium pan, melt 1 tablespoon of butter and sauté the thinly sliced leeks over medium heat until they become tender, about 5 to 7 minutes.
  3. Add Garlic: Add the minced garlic to the pan with the leeks and continue to sauté for another 1 to 2 minutes until fragrant.
  4. Set Leeks Aside: Remove the sautéed leeks and garlic from the pan and set aside for later layering.
  5. Make the Roux: In the same pan, melt the remaining 2 tablespoons of butter over medium heat. Stir in the flour and cook until the butter is fully absorbed, forming a smooth paste.
  6. Add Milk Gradually: Slowly whisk in the whole milk to the flour mixture, continuously stirring to create a smooth sauce without lumps.
  7. Season the Sauce: Add salt, black pepper, dry mustard powder, and thyme to the sauce. Continue heating and stirring until the sauce thickens and becomes smooth. Taste and adjust seasoning as needed, then remove from heat.
  8. Assemble the Gratin: In the prepared baking dish, layer the ingredients in thirds: start with one-third of the sliced potatoes, all of the leeks, and one-third of the sliced carrots. Sprinkle one-third of the shredded cheese over the vegetables, then pour one-third of the sauce on top. Repeat the layering process two more times, finishing with the sauce on the top layer.
  9. Bake Covered: Cover the dish and bake in the preheated oven for 30 minutes to allow the vegetables to cook and the flavors to meld.
  10. Uncover and Continue Baking: Remove the cover and bake for an additional 25 to 30 minutes until the vegetables are tender and the top is golden and bubbly. Test tenderness by inserting a knife through the layers.
  11. Rest and Garnish: Remove the gratin from the oven and let it rest for 10 minutes to set. Garnish with the fresh chopped chives or parsley before serving.

Notes

  • For thinner slices and faster cooking, use a mandoline to slice potatoes, carrots, and leeks uniformly.
  • Feel free to mix cheeses according to your preference for a more complex flavor.
  • Use whole milk for a richer sauce, but 2% milk can be substituted for a lighter version.
  • Covering the dish initially helps steam the vegetables thoroughly before crisping the top uncovered.
  • Leftovers can be refrigerated and reheated; add a splash of milk when reheating if sauce thickens.

Find it online: https://recipefeastful.com/leek-carrot-and-potato-au-gratin-recipe/