Roll up breast of lamb (I cut whole breast into two, and rolled these up separately, cooks a bit quicker) .
Put on top of sliced onions in pan.
Half cover with lamb gravy (best use E Cuisine Home Chef lamb stock cos its the only lamb stock worth using) put in oven gas mk 4, covered with foil.
Bake for 3 hours, basting from time to time.
Take out, rest, and while it is resting, add 1 tablespoon of blackberry vinegar and reduce until syrupy. Onions will have melted into the gravy.
Cut each half breast into two pieces and put on plate, cover with gravy.