One of my early dishes at Sepia restaurant, tender beefy flat iron steak is paired with knob onions (which are less fussy than pearl onions and roast up beautifully), maitake mushrooms (which I love for their deep Earthy flavor and striking appearance) and a rich Béarnaise sauce. At Sepia we would accompany this dish a slightly sweet and savory coffee soil and, to go completely over the top, bone marrow beignets dusted with roasted beef fat powder. (DM me if you are ambitious enough to want that recipe too!)

Serving for 4 people 

Ingredients:

• 12 fingerling potatoes, halved lengthwise (try to get potatoes that are similar in size)
• 8 sprigs thyme (divided)
• 2 cloves garlic, in the skins
• 2 cups rendered duck fat (or substitute 2 cups good-quality lard or extra-virgin olive oil)
• 4 flat iron steaks (12 ounces each; see note)
• Salt and pepper to taste
• 1 large turnip, peeled, cut into ¼-inch slices; cut slices into four parts then cut each part into a 1 ½-inch disc
• 2 clusters maitake mushrooms, cut into 8 slabs, ¾ to 1 inch thick (see note)
• 8 knob onions, trimmed to 2 ½ inches long, cut in half lengthwise (see note)
• Béarnaise sauce (see recipe bellow)
• Coffee Soil (see recipe bellow)

Directions:

1. Make the coffee soil and set it aside. (It will keep for several days).
2. In a medium saucepan, combine potatoes, half the thyme, garlic and duck fat.
3. Heat the fat to a gentle simmer and cook potatoes until just tender. Cooking time will depend on size of potatoes. Remove potatoes and set aside. Drain off fat, discarding solids and reserving fat. You will need some later in the recipe. The rest can be used for other dishes.
4. At least 1 hour before cooking, remove meat from refrigerator and season with salt and pepper. You do not want to cook the meat right out of the refrigerator as it will cook faster and more evenly if it is not cold.
5. Preheat a grill. (For this recipe, gas will work but hardwood charcoal is better.)
6. Make the béarnaise and keep it in a warm place.
7. Lightly oil the grill and put the steaks on to cook. They will take 6 to 8 minutes per side depending on how hot your fire is. Cook them to 125 degrees. (If you take the steak off at that temp and rest, you will have a steak that will reach to about 129 to 131 degrees, the end of rare and very beginnings of medium-rare. For a true rare steak, you should pull it off the heat at 121 to 122 degrees. Remember, you can always cook it a little more if you don’t like it, but you can’t cook it less.)
8. When done, let rest on a wire rack over a sheet pan for at least 5 minutes before serving.
9. While steaks are cooking, heat a large saute pan. Add 3 tablespoons of the reserved duck fat and, when hot, start arranging the turnips, mushrooms and onions in the pan cut sides down. (This will help encourage even browning. If you do not have a very large pan, you may have to cook vegetables in batches.) Add remaining thyme and season vegetables with salt and pepper. Cook until vegetables are lightly browned and cooked through, turning as needed.

Coffee Soil:

• ½ cup sugar
• ½ cup almond flour
• 1/3 cup all-purpose flour
• 2 tablespoons unsweetened cocoa powder
• 1 ½ tablespoons coffee grounds
• 6 tablespoons (¾ stick) butter, melted
• ½ teaspoon kosher salt

Directions:

1. Preheat oven to 300 degrees.
2. Combine all ingredients in a bowl and mix well with hands.
3. Spread evenly in an ovenproof pan and bake in preheated oven 12 to 15 minutes.
4. Cool completely before grinding in a food processor.

Béarnaise Sauce:

• 2 medium shallots, minced
• ¼ cup dry white wine 
• ¼ cup white-wine vinegar 
• 10 crushed black peppercorns 
• 4 large sprigs of fresh tarragon 
• Salt to taste
• 1 ¼ cups (2 ½ sticks) good-quality unsalted butter
• 3 large egg yolks 
• 3 tablespoons water 
• Freshly ground pepper to taste 
• 3 tablespoons finely chopped tarragon

Directions:

1. To make the reduction: In a heavy-bottomed saucepan, combine shallots, wine, vinegar, peppercorns, tarragon and salt and simmer over medium-high heat until two tablespoons liquid remain. Strain and discard the solids. Set aside.
2. To make sauce: In a heavy saucepan, clarify the butter. Set aside.
3. Bring a medium-size pot of water to a simmer.
4. Put the egg yolks and water in a heavy-duty metal mixing bowl that is large enough to sit atop the pan of water.
5. Off the stove, whisk the egg yolks and water 30 seconds, whipping in lots of air.
6. Set bowl over pan of water, holding one edge with a kitchen towel. Cook, whisking constantly and scraping the bowl, until thick and voluminous. This will take 2 to 3 minutes. The whisk will leave tracks that hold for a few seconds. Do not cook too long or mixture will get too thick.
7. Remove from heat and whisk rapidly 30 seconds to cool it slightly. Add the reserved clarified butter, a little at a time, whisking constantly. Be sure the butter isn’t too hot or it will break the emulsion.
8. To finish the sauce, whisk in 1 tablespoon of the reserved reduction (or more to taste). Season with salt and pepper. Stir in finely chopped tarragon. Serve warm.

To serve:

Remove thyme from vegetables in pan. Arrange vegetables, along with the reserved potatoes and the steaks, on four dinner plates. Scatter some of the coffee soil around the steaks and serve the béarnaise on the side.

Notes: 

Maitake mushrooms and knob onions are not available locally year-round. For the mushrooms, you can substitute portobellos or shiitakes. If using the smaller mushrooms, use ¼ to ½ pound. For the onions, cippolini, small boiler onions or pearl onions can be used.

Flat iron stakes may have to be special-ordered but any streak you like can easily be substituted.