1 tbspMoutarde de Dijon
1 (14 1/2 oz) piece of flat iron steak
1 bunch scallions
kosher salt and freshly ground black pepper, to taste
2 tbsp olive oil
1 sprig rosemary and 1 sprig thyme
1 cup all-purpose flour
3 eggs, lightly beaten, plus 2 egg yolks
1 cup panko breadcrumbs
2 large green tomatoes, sliced 1/2-inch thick
1 1/4 cups safflower oil, plus more for frying
2 tbsp white wine vinegar
1 tbsp prepared horseradish
1/2 cup extra-virgin olive oil
1 bunch chives, finely chopped
1 large baguette, halved lengthwise
1 cup watercress leaves
Heat a grill pan over high. Season steak and scallions generously with salt and pepper and drizzle with oil. Cook steak along with the rosemary and thyme until cooked to desired doneness and cook scallions until charred. Transfer steak to a plate to rest and transfer scallions to a cutting board.
Roughly chop scallions.
Heat a 12-inch skillet over medium-high and add foie gras. Cook, turning once, until golden on each side, about 2 minutes. Transfer foie gras to a plate and pour the fat from the pan over the steak.
Place flour, beaten eggs, and panko in 3 separate shallow dishes. Toss the tomato slices in the flour, then the egg, then the breadcrumbs and place on a plate. Wipe the skillet clean and heat safflower oil. Cook the tomatoes, flipping once, until golden and crispy, about 3 minutes. Transfer to a paper towel-lined plate and season with salt.
In a medium bowl, whisk together the egg yolks, vinegar, mustard, and horseradish. Slowly drizzle in the 1 1/4 cups safflower oil and the olive oil until thick. Stir in the chives and set mayonnaise aside.
Thinly slice the steak and pour the resting juices into the mayonnaise. Smear mayonnaise on the insides of the baguette and top with watercress, fried tomatoes, steak, foie gras, and scallions. Top with bread and get into it.