How to Make It
Stir together cocoa, espresso powder, salt, and pepper in a small bowl. For each serving, generously coat 1 (12-oz.) steak on all sides with 1 to 2 teaspoons of the cocoa rub. Heat a large cast-iron skillet over high. Add steak, and cook each side to desired degree of doneness, about 3 minutes per side for medium. Store remaining cocoa rub in an airtight container for up to 2 months.