1 teaspoon (5 grams) freshly ground black pepper, plus more
750–800 grams flank steak
In a medium bowl, whisk together coffee, molasses, mustard, olive oil and vinegar.
Add onion, garlic, ginger, salt and pepper; whisk to combine.
Pour marinade into a large re-sealable bag. Add steak, rosemary and thyme sprigs. Seal, remove as much air as possible and turn steak to coat evenly. Place re-sealable bag on a rimmed baking sheet and refrigerate for four to eight hours. Remove from fridge 30 minutes before cooking.
Heat broiler to high and set a rack 15 centimeters from broiler.
Remove steak off rimmed sheet and line sheet with a roasting rack. Remove steak from marinade bag, shake off any excess and place on prepared rack. Season with salt and pepper.
Broil until 120°F to 125°F (50°C), about eight to 12 minutes, flipping halfway. Set the steak aside to rest for ten minutes under foil before slicing against the grain and serving.