Peel the onions and cut into half onion rings. Wash the rosemary sprigs and pat dry. Pluck the rosemary needles from the branch and chop finely. Peel the garlic and cut into fine slices.
Put the olive oil in a hot pan and sauté the onions, garlic and rosemary needles. Deglaze with half a bottle of black beer and simmer for about 5 minutes. Take the pan off the stove. Stir in the mustard, honey and pepper and let cool.
Put the cooled marinade in a bowl and mix with the rest of the black beer. Put the neck steaks in and leave to work overnight. Grill the steaks on both sides on the grill.