Stuffed & Seared Chicken Thighs With Refrigerator-Door Mustard

INGREDIENTS

Anchovy, fillets

sprig Thyme or oregano, fresh

1/2 cup

Capers

1 1/2 tsp

Dijon mustard

1 1/2 tbsp

Mustard, whole-grain

4 tbsp

Refrigerator-door mustard

2 tbsp

Peppercorns, green in brine

2 tsp

Sea salt, coarse

1 tsp

Grapeseed or canola oil

2 tbsp

Butter, unsalted

Boneless* (see note below), skin-on chicken thighs (about 1 1/3 pounds)