Ingredients
1/4 cup sour cream
1/4 cup mayonnaise
2 tablespoons prepared horseradish
1 tablespoon grainy mustard
Coarse salt and freshly ground black pepper
1 1/2 pounds flank steak
3 tablespoons extra-virgin olive oil
1 bunch watercress, tough stems trimmed
1 tablespoon freshly squeezed lemon juice
4 thick slices rustic bread, toasted
Roasted Peppers with Garlic and Basil, or store-bought roasted bell peppers, if you prefer
Preparation
Make horseradish sauce: In a small bowl, whisk together sour cream, mayonnaise, horseradish, and mustard. Season with salt and pepper. Cover with plastic wrap; refrigerate while preparing steak.
Heat broiler, with rack 6 inches from heat. Season steak well on both sides with salt and pepper; rub with 2 tablespoons oil. Place on a roasting pan fitted with a rack. Broil 6 minutes on each side for medium-rare. Let rest 5 minutes before slicing 1/4 inch thick.
Place watercress in a bowl; toss with remaining tablespoon oil and the lemon juice. Season with salt and pepper. Serve on toasted bread, topped with steak, horseradish sauce, and roasted peppers.
