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brussels sprouts gratin steak

Brussels Sprouts Gratin with Steak

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Prep Time 20 minutes
Cook Time 35 minutes
Resting Time 5 minutes
Total Time 1 hour
Course Main
Cuisine American
Servings 4 servings

Equipment

  • 1 large oven-safe skillet or 1 baking dish (9x13)
  • 1 large skillet for steak if not using oven-safe
  • 1 Medium saucepan
  • 1 Mixing bowl
  • 1 Cutting board
  • 1 Chef's knife
  • 1 Whisk
  • 1 Tongs
  • 1 Measuring cups set
  • 1 Measuring spoons set
  • 1 sheet pan optional for finishing steak
  • 1 aluminum foil sheet

Ingredients
  

  • 1 1/2 pound Brussels sprouts trimmed and halved
  • 2 tablespoon olive oil
  • 1 teaspoon kosher salt divided
  • 1/2 teaspoon black pepper divided
  • 1 tablespoon unsalted butter
  • 1 small yellow onion finely diced
  • 2 clove garlic minced
  • 1 cup heavy cream
  • 1/2 cup whole milk
  • 1 teaspoon Dijon mustard
  • 1/4 teaspoon nutmeg freshly grated
  • 3/4 cup Gruyère cheese shredded
  • 1/2 cup Parmesan cheese grated
  • 1/2 cup panko breadcrumbs
  • 1 tablespoon olive oil for breadcrumbs
  • 1 1/2 pound ribeye or New York strip steak 1–1 1/4 inches thick
  • 1 tablespoon neutral high-heat oil
  • 1 teaspoon fresh thyme leaves chopped
  • 1 teaspoon fresh rosemary chopped
  • 1 tablespoon unsalted butter for basting
  • 1 teaspoon flaky sea salt for finishing, optional

Instructions
 

  • Preheat the oven to 425°F (220°C).
  • Toss Brussels sprouts with 2 tablespoons olive oil, 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper, then spread cut-side down in a large oven-safe skillet or baking dish.
  • Roast Brussels sprouts for 15–18 minutes until edges are browned and centers are just tender, then reduce oven to 400°F (205°C).
  • Meanwhile, season steak on both sides with remaining 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper and let sit at room temperature for 15 minutes.
  • In a saucepan over medium heat, melt 1 tablespoon butter, add diced onion, and cook 3–4 minutes until translucent.
  • Stir in garlic and cook 30 seconds until fragrant.
  • Whisk in heavy cream, milk, Dijon, and nutmeg, bring to a gentle simmer for 2–3 minutes, and remove from heat.
  • Stir Gruyère and half the Parmesan into the hot cream until melted and smooth.
  • In a bowl, mix panko with 1 tablespoon olive oil and the remaining Parmesan.
  • Pour cheese sauce over roasted Brussels sprouts, top evenly with panko mixture, and return to the oven at 400°F for 12–15 minutes until bubbling and golden.
  • While gratin bakes, heat a large skillet over medium-high until just smoking, add neutral oil, and sear steak 2–3 minutes per side until deep brown.
  • Add butter, thyme, and rosemary to the skillet and baste steak for 30–60 seconds per side, then transfer to a cutting board to rest for 5 minutes.
  • Tent steak loosely with foil while resting and slice against the grain into 1/2-inch slices.
  • Remove gratin from oven and let stand 5 minutes to set, then season with flaky sea salt if using.
  • Serve sliced steak alongside or over portions of Brussels sprouts gratin.

Notes

For even caramelization, choose similarly sized Brussels sprouts and keep cut sides down during the initial roast. If you prefer a milder gratin, swap half the Gruyère for mozzarella or fontina, and for added depth, crisp 3–4 slices of chopped bacon before the onions and use the drippings to start the sauce. A quick steak doneness guide: about 125°F for rare, 130–135°F for medium-rare, and 140°F for medium; use an instant-read thermometer and pull 5°F before target as carryover heat finishes cooking. If your skillet isn’t oven-safe, transfer sprouts to a greased baking dish before saucing. The breadcrumb topping can be toasted in a dry pan first for extra crunch, and leftovers reheat well at 350°F covered for 10–12 minutes.
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