1/2 cup Dijon mustard
1/4 cup dry white wine
4 teaspoons olive oil
2 teaspoons Worcestershire sauce
2 lb. small boneless, skinless chicken thighs (about 8 to 10), trimmed
2 tablespoons margarine
3/4 cup panko
3 large garlic cloves, minced
1/4 teaspoon cayenne; more to taste
Kosher salt and freshly ground black pepper
Combine the mustard, wine, oil, and Worcestershire in a 9×13-inch baking dish. Add the chicken, turn to coat well, and set aside for 15 minutes.
Meanwhile, in a 10-inch skillet, heat the margarine over medium-low heat. Add the panko and cook, stirring, until light golden, about 4 minutes. Add the garlic and cook until the crumbs are golden brown, about 1 minute more. Season with the cayenne, 1/2 tsp. salt, and 1/4 tsp. pepper. Set aside to cool.
Heat a grill pan over medium-high heat. Lay the thighs flat on the grill and cook, turning once, until just cooked through, about 5 minutes per side. Transfer to a large platter and let rest for a few minutes. Sprinkle crumbs over the chicken, and serve.