1 teaspoon (5g) freshly ground black pepper, plus more
750–800 g (approx. 1 3/4lb) flank steak
In a medium bowl, whisk together coffee, molasses, mustard, olive oil and vinegar.
Add onion, garlic, ginger, thyme, rosemary, salt and pepper; whisk to combine.
Pour marinade into a large resealable bag and add steak. Seal, remove as much air as possible and turn to coat steak. Place resealable bag on a rimmed baking sheet and refrigerate for 4 to 8 hours. Remove from fridge 30 minutes before cooking.
Heat broiler to high and set a rack 6-inches (15cm) from broiler.
Remove steak from rimmed sheet and line sheet with a roasting rack. Remove steak from marinade, shake off any excess and place on prepared sheet. Season with salt and pepper.
Broil until 120 to 125F (50C), about 8 to 12 minutes, flipping halfway. Set the aside steak to rest for 10 minutes under foil before slicing against the grain to serve.