Grilled Flat Iron Steak Recipe

Bring steak to room temperature

Remove the flat iron steak from the refrigerator 30–45 minutes before cooking so it comes to room temperature; pat dry with paper towels.

Season both sides of the steak evenly with kosher salt and freshly ground black pepper. Lightly brush with 1 tablespoon olive oil.

Preheat a grill or heavy skillet (cast iron) over high heat until very hot (about 450–500°F / 230–260°C). Add 1 tablespoon unsalted butter to the pan if using stovetop; allow it to melt and foam.

Place the steak on the grill or in the hot skillet. Cook undisturbed 3–4 minutes per side for medium-rare (internal temp 125–130°F / 51–54°C). Adjust time for desired doneness. For a 1 lb flat iron expect 6–9 minutes total depending on thickness.

Remove steak to a cutting board and tent loosely with foil. Rest 8–10 minutes so juices redistribute before slicing thinly against the grain.

While the steak rests, make the sauce. In a medium skillet, heat 1 tablespoon olive oil and 1 tablespoon unsalted butter over medium heat until the butter foams.

Add the finely minced shallots and cook until softened and translucent, about 2 minutes. Add the minced garlic and cook 30 seconds until fragrant, taking care not to brown it.

Increase heat to medium-high and add the sliced mushrooms. Sauté until they release their liquid and begin to brown, about 4–5 minutes.

Stir in 1 tablespoon tomato paste and cook 1 minute to deepen flavor. Add the diced tomatoes and stir to combine.

Pour in 1 cup dry white wine and bring to a simmer, scraping up any browned bits from the pan. Reduce the wine by about half, 3–5 minutes.

Add 1 cup beef demi-glace or beef stock, stir, and simmer until the sauce thickens slightly, about 4–6 minutes.

Reduce heat to low and stir in chopped fresh tarragon and parsley. Season with salt and 1/2 teaspoon black pepper (taste and adjust). Keep warm until plating.

If you prefer a silkier finish, swirl in an additional 1/2 tablespoon cold butter off the heat to enrich the sauce before serving.

Bring a medium pot of salted water to a rolling boil. Add the trimmed haricot verts and blanch 2 minutes until bright green and just tender.

Immediately transfer the beans to a bowl of ice water to stop cooking; drain and pat dry.

In a sauté pan over medium heat, melt 1 tablespoon unsalted butter. Add the drained haricot verts and toss until warmed through, 1–2 minutes. Season with 1/2 teaspoon salt, 1/4 teaspoon black pepper, and lemon zest if using. Keep warm.

Place the potato chunks in a medium pot and cover with cold water. Bring to a boil and cook until very tender, 12–15 minutes. Drain thoroughly.

Return potatoes to the pot, add 1 tablespoon butter, 1/4 cup milk, 3/4 teaspoon salt and 1/4 teaspoon black pepper. Mash until smooth and let cool slightly.

Stir in 1/2 cup grated Gruyère (or cheddar). Shape the mashed potato mixture into 8 small croquettes (about 1.5 tablespoons each) or 6 larger ones.

Set up a dredging station: place 1/2 cup flour in one shallow bowl, the beaten egg in a second, and 3/4 cup breadcrumbs in a third. Lightly coat each croquette in flour, tap off excess, dip in beaten egg, then roll in breadcrumbs to evenly coat.

In a sauté pan over medium heat, add vegetable oil to reach about 1/8–1/4 inch depth. Heat until shimmering but not smoking (about 325–350°F). Fry croquettes in batches 2–3 minutes per side until golden brown and crisp. Drain on paper towels and keep warm in a low oven (200°F / 95°C) while finishing others.

Alternatively, for a lighter finish, spray croquettes with oil and bake at 425°F for 12–15 minutes, turning once, until browned.

Slice the rested flat iron steak thinly against the grain into 1/4-inch slices.

Place a portion of haricot verts and two or three cheesy potato croquettes on each plate. Fan sliced steak alongside or atop the vegetables.

Spoon the warm sauce chasseur generously over the steak and mushrooms, finishing with a sprinkle of chopped fresh tarragon or parsley if desired. Serve immediately.