Spring Leek and Mushroom Gratin is the ultimate spring comfort food dish. Serve alongside your protein of choice for a lovely brunch or dinner.
This post is in partnership with Sprouts Farmers Market and Horizon Organic. I was compensated for my time, however all opinions are my own.
Today, we’re transforming a humble vegetable into something beyond delicious. Leeks may be the wallflowers of alliums, however, they become magic wands in this dish. Because leeks have a sweeter, more delicate flavor than onions, they are extremely versatile during spring, which is when their flavor peaks.
In this seasonal gratin, leeks are teamed up with shiitake mushrooms and lots of garlic for big flavor and texture. Additionally, a crunchy, cheesy breadcrumb topper marks a breakthrough moment for the roasted veggies.
Which Part of The Leek Do I Use?
Since just the white and light green parts of a leek are tender (the tough dark green leaves are too tough to eat, but make a great stock), it’s best to slice the leeks at both ends. To do this, start by cutting off the dark green leaves and trim to the part where the color is a pale green. Next, cut off the root end at about ½ inch into the white stem. At this point, you should be left with a 6- to 8-inch tube.
How Do I Cook Leeks?
In short, leeks are ultra versatile and can be either roasted, sautéed, caramelized, or grilled. Just be sure to slice the leeks with the grain, as opposed to cross-wise, which prevents them from falling apart and turning to mush after being cooked.
For this recipe, we give the leeks a quick boil to soften their fibers before roasting, which helps render their texture silky and flavor sweet.
Next, let’s shift gears to the creamy, cheesy elements, shall we?
Why Grass-Fed Dairy?
When it comes to milk, cheese, and butter, I ante up for organic grass-fed dairy. (Grass-fed organic dairy differs from standard organic in that it comes from cows whose diet includes mainly organic grass). My go-to brand in terms of taste, quality, and nutrition has been Horizon Organic® dairy products, which are made from pasture-raised cows not given hormones, antibiotics, or toxic pesticides.
In addition, I used Horizon Organic Unsalted Butter in this recipe for a double dose of quality dairy. Look for Horizon Organic products (which includes their new Grass Fed Milk and Protein Milk) at Sprouts Farmers Market.If you make this recipe, be sure to share on Instagram and tag @dishingouthealth and #dishingouthealth so I can see your beautiful creations! Additionally, I’d love if you could leave a review on the post and share with your friends.
Other Healthy Spring Side Dishes:
Spring Leek and Mushroom Gratin
- 3 leeks white and pale green parts only (see above for trimming instructions)
- 2 Tbsp. extra-virgin olive oil
- 6 oz. shiitake mushrooms stemmed and sliced
- 1 tsp. kosher salt divided
- 2. Tbsp. unsalted butter
- 4 garlic cloves minced
- 2 Tbsp. flour
- 2 ½ cups Horizon Organic Grass Fed Vitamin D Milk
- 1 Tbsp. fresh thyme leaves plus more for garnish
- 1 tsp. freshly ground black pepper
- 2 tsp. fresh lemon juice
- ¾ cup panko-style breadcrumbs
- ¼ cup freshly grated Parmesan cheese
- Preheat oven to 375°F. Bring a large pot of water to a boil and fill a bowl with ice water. Add leeks to boiling water and cook for 3 minutes. Shock the leeks by transferring to the ice-water bath. Drain and slice leeks in half lengthwise.
- Heat oil in an oven-safe cast-iron skillet or cocotte over medium heat. Add mushrooms and cook 3 to 5 minutes, stirring occasionally, until golden and slightly tender. Season with ¼ tsp. salt and transfer mushrooms to a bowl.
- Add butter and garlic to pan; cook 1 minute. Sprinkle in flour and whisk continuously for 30 seconds. Gradually stream in milk, whisking constantly, until combined. Increase heat to bring mixture to a simmer; cook 2 to 3 minutes, until slightly thickened. Add mushrooms back to skillet, along with thyme, remaining ¾ tsp. salt, black pepper, and 1 tsp. lemon juice. Lay sliced leeks across the top of gratin, gently pressing to slightly submerge in milk mixture. Sprinkle breadcrumbs and Parmesan cheese overtop. Transfer to oven and bake for 35 to 40 minutes, until golden and bubbly.
- Squeeze remaining 1 tsp. lemon juice overtop and garnish with additional fresh thyme before serving.