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″ skillet over medium heat, melt 2 tablespoons butter. Add sliced onions and 1 teaspoon kosher salt; cook, stirring occasionally, until onions are deeply golden and jammy, about 35 to 50 minutes.

Step 2: Add thyme sprigs and white wine, cooking while stirring and scraping the pan until liquid reduces and onions become jammy again, about 1 to 2 minutes. Season with freshly ground black pepper, transfer onions to a bowl, and let cool. Wipe out the pan.

Step 3: Arrange a rack in the center of your oven and preheat to 350°F (175°C). Place cabbage wedges on a baking sheet and season all over with 1 teaspoon 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 remaining 1/4 teaspoon salt. Stir frequently until breadcrumbs are golden brown, about 3 to 4 minutes. Transfer to a small bowl and wipe out the skillet.

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

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

Step 7: Fold 1 cup shredded Gruyère and three-quarters of the caramelized onions into the cream sauce. Nestle cabbage wedges back into the skillet and spoon sauce evenly over them. Top with remaining caramelized onions, sprinkle with remaining 1/2 cup cheese, and half the toasted breadcrumbs.

Step 8: Transfer skillet to the oven and bake until cabbage is tender and gratin is bubbly, about 40 minutes. Just before serving, sprinkle with remaining breadcrumbs and thyme leaves, and season with additional pepper as desired.

Tips & Variations

Make caramelized onions up to three days ahead and store in the refrigerator to save time on baking day.

For a nuttier flavor, try substituting Gruyère with a mix of Swiss and Parmesan cheeses.

Use a cast-iron skillet for even heating and a beautiful crust, but any ovenproof skillet will work.

Add a pinch of nutmeg to the cream sauce for subtle warmth and depth.

FAQs

Can I use a different type of cabbage?

Yes, green cabbage works best due to its sweetness and texture, but savoy or napa cabbage can be used for a slightly different flavor and tenderness.

Is it possible to make this recipe dairy-free?

You can substitute butter with a dairy-free alternative and use plant-based cream and milk substitutes. For cheese, try a vegan Gruyère-style cheese or nutritional yeast for a cheesy flavor.