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Spring Leek and Mushroom Gratin Recipe

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4.2 from 7 reviews

This Spring Leek and Mushroom Gratin is a creamy, flavorful casserole featuring tender leeks and earthy shiitake mushrooms in a rich thyme-infused béchamel sauce, topped with crispy panko breadcrumbs and Parmesan cheese. Perfect as a hearty side or light main dish, this gratin offers a comforting and elegant way to celebrate fresh spring vegetables.

  • Total Time: 1 hour
  • Yield: 6 servings

Ingredients

Vegetables and Herbs

  • 3 leeks (white and pale green parts only, cleaned and trimmed)
  • 6 oz. shiitake mushrooms, stemmed and sliced
  • 4 garlic cloves, minced
  • 1 tbsp. fresh thyme leaves, plus more for garnish

Dairy and Fats

  • 2 tbsp. unsalted butter
  • 2 ½ cups Horizon Organic Grass Fed Vitamin D Milk
  • ¼ cup freshly grated Parmesan cheese

Dry Ingredients

  • 2 tbsp. all-purpose flour
  • ¾ cup panko-style breadcrumbs
  • 1 tsp. kosher salt (divided)
  • 1 tsp. freshly ground black pepper

Oils and Seasonings

  • 2 tbsp. extra-virgin olive oil
  • 2 tsp. fresh lemon juice (divided)

Instructions

  1. Prepare Leeks: Preheat the oven to 375°F. Bring a large pot of water to a boil and prepare an ice water bath. Add the leeks to the boiling water and cook for 3 minutes to soften slightly. Immediately transfer the leeks to the ice water bath to stop the cooking process. Drain and slice the leeks lengthwise in half.
  2. Cook Mushrooms: Heat olive oil in an oven-safe cast-iron skillet or cocotte over medium heat. Add the shiitake mushrooms and cook for 3 to 5 minutes, stirring occasionally, until they are golden and slightly tender. Season with ¼ teaspoon kosher salt. Remove mushrooms from skillet and set aside.
  3. Make Béchamel Sauce with Mushrooms: Add the unsalted butter and minced garlic to the skillet and cook for 1 minute until fragrant. Sprinkle the flour over the butter and garlic, whisking continuously for 30 seconds to form a roux. Gradually add the milk while whisking constantly until smooth. Increase the heat to bring the mixture to a simmer and cook for 2 to 3 minutes until the sauce thickens slightly. Return the mushrooms to the skillet and stir in the fresh thyme, remaining ¾ teaspoon salt, black pepper, and 1 teaspoon lemon juice.
  4. Assemble Gratin: Lay the sliced leeks evenly over the mushroom and béchamel mixture in the skillet, pressing them gently to submerge slightly into the sauce. Sprinkle the panko breadcrumbs evenly over the top, followed by the grated Parmesan cheese.
  5. Bake: Transfer the skillet to the preheated oven and bake for 35 to 40 minutes until the gratin is golden brown on top and bubbling around the edges.
  6. Finish and Serve: Remove the gratin from the oven, squeeze the remaining 1 teaspoon of lemon juice over the top, and garnish with additional fresh thyme leaves. Serve warm.

Notes

  • To clean leeks thoroughly, cut off the roots and dark green tops, slice lengthwise, and rinse under running water to remove grit.
  • If you don’t have a cast-iron skillet, an oven-safe baking dish will work as well.
  • Panko breadcrumbs create a crispier crust than traditional breadcrumbs; substitute with regular if unavailable.
  • This dish can be prepared a day ahead and reheated gently in the oven.
  • Adjust seasoning to taste, particularly salt and pepper, depending on the saltiness of your Parmesan.
  • Author: Daisy
  • Prep Time: 15 minutes
  • Cook Time: 45 minutes
  • Category: Side Dish
  • Method: Baking
  • Cuisine: French-inspired
  • Diet: Vegetarian

Find it online: https://dishiary.com/spring-leek-and-mushroom-gratin-recipe/