Ingredients

2 tbsp. unsalted butter

2 large yellow onions, thinly sliced into half-moons

1 tsp. kosher salt

2 thyme sprigs

1/3 cup dry white wine

Freshly ground black pepper

1 small head of green cabbage (about 2 lb.), cut into 6 wedges

1 1/4 tsp. kosher salt

4 tbsp. unsalted butter, divided

1/2 cup panko breadcrumbs

4 tbsp. neutral oil, divided

2 tbsp. all-purpose flour

1 1/2 cups heavy cream

1 1/2 cups whole milk

1 1/2 cups shredded Gruyère, divided

Instructions

Step 1: In a straight-sided 12-inch skillet over medium heat, melt 2 tablespoons butter. Add thinly sliced onions and 1 teaspoon kosher salt. Cook, stirring occasionally, until the onions are jammy and deep golden brown, about 35 to 50 minutes.

Step 2: Add thyme sprigs and white wine. Stir and scrape the pan to release browned bits. Cook until the liquid is reduced and onions are jammy, 1 to 2 minutes. Season with freshly ground black pepper. Transfer onions to a clean bowl and let cool. Wipe out the pan.

Step 3: Preheat oven to 350°F and arrange a rack in the center. Spread cabbage wedges on a baking sheet and season with 1 teaspoon kosher salt. Let sit for 10 minutes.

Step 4: In a large ovenproof skillet over medium heat, melt 2 tablespoons butter. Add panko breadcrumbs and season with the remaining 1/4 teaspoon kosher salt. Cook, stirring frequently, until breadcrumbs are golden brown, about 3 to 4 minutes. Transfer to a small bowl and wipe out the skillet.

Step 5: Over medium-high heat, heat 2 tablespoons neutral oil in the same skillet. Pat cabbage wedges dry with paper towels. Add half the wedges flat side down and sear until golden brown, 2 to 3 minutes. Flip and cook the other flat side until golden brown, about 2 minutes more. Return cabbage to the baking sheet. Repeat with remaining 2 tablespoons oil and cabbage wedges. Wipe out the skillet.

Step 6: Return skillet to medium heat and melt remaining 2 tablespoons butter. Add flour and cook, stirring constantly, until a bubbling blonde paste forms, about 1 minute. Whisk in heavy cream and whole milk. Bring to a boil over medium-high heat, then reduce heat to medium and cook, stirring occasionally, until sauce is reduced and slightly thickened, 5 to 7 minutes.

Step 7: Remove from heat and fold in 1 cup shredded Gruyère and three-quarters of the caramelized onions.

Step 8: Nestle cabbage wedges back into the skillet. Spoon the sauce evenly over the cabbage. Top with the remaining caramelized onions. Sprinkle with the remaining 1/2 cup cheese and half of the toasted breadcrumbs.

Step 9: Transfer the skillet to the oven and bake until cabbage is tender, about 40 minutes. Remove from oven and top with the remaining breadcrumbs and thyme sprigs. Season with freshly ground black pepper to taste before serving.

Tips & Variations

Make the caramelized onions up to 3 days ahead and store in an airtight container in the refrigerator to save time on the day you prepare the gratin.

For a sharper flavor, substitute half the Gruyère with aged cheddar or Parmesan cheese.

If you don’t have thyme, rosemary or sage can be used as aromatic alternatives.

Use a cast-iron skillet if possible for even heat and easy stovetop to oven transfer.

FAQs

Can I use a different type of cabbage?

Yes, green cabbage works best for its sweetness and texture, but you can use Savoy or Napa cabbage for a milder taste and softer leaves.

Is it possible to make this dish dairy-free?

To make a dairy-free version, substitute butter with plant-based margarine or oil, use coconut or oat cream instead of heavy cream and milk, and choose a dairy-free cheese alternative for the topping.