Grilled Steak and Radishes with Mustard Butter

 

2 T. olive oil, plus more for the grill

4 T. (½ stick) unsalted butter, at room temperature

2 tsp. Dijon mustard

Kosher salt

1 T. finely chopped fresh flat-leaf parsley (optional)

1½ to 2 pounds hanger steak (about 1 inch thick) or skirt steak (about ½ inch thick)

Freshly ground black pepper

8 to 12 radishes, preferably with green tops attached, halved lengthwise

 

Prepare a grill or grill pan for high heat. Lightly oil the grill grate with olive oil. In a small bowl, stir together the butter, mustard, ½ tsp. kosher salt, and the parsley, if using. Set aside. Season the steak generously with salt and pepper, using 1 tsp. salt and ¾ tsp. pepper for each pound of meat. Grill, turning once, until nicely charred all over, about 5 minutes per side for medium-rare hanger steak, or 3 to 4 minutes per side for medium-rare skirt steak. (If you’re using an instant-read thermometer to check doneness, aim for 130°F.) Transfer the steak to a cutting board and let it rest for 10 minutes. Meanwhile, drizzle the radish bulbs and greens with 2 T. olive oil and season with ½ tsp. salt and ¼ tsp. pepper. Reduce the grill heat to medium-high. Grill the radishes until the bulbs are crisp-tender and the greens are a little charred, 2 to 4 minutes per side, depending on the size of your radishes. Slice the steak against the grain. Arrange on a serving platter with the radishes. Serve the steak and radishes warm, with the mustard butter spooned over the top.