1.6 kg/3lb 8oz onions, thinly sliced
2 tbsp chopped fresh parsley
2-3 tbsp anchovy essence (or several finely chopped anchovies), or to taste
1 bay leaf
1 tbsp red wine vinegar
2 tbsp dripping or vegetable oil
fine salt and freshly ground white pepper
1.6 kg/3lb 8oz lamb breast, boned, rolled and tied with kitchen string