Trim the spinach, rinse in water several times, cook for 10 minutes in salted boiling water and drain. Lay the 3 slices of ham in an ovenproof dish, surround with the spinach and bake in a low oven until the fat turns translucent. Meanwhile, chop and sweat the shallots in 1 3/4 oz of butter, add the vinegar and reduce almost completely. Add the stock cube, diluted in hot water, and reduce again by a quarter. Take off the stove and blend in the butter, in small chunks, using a whisk. Coat the hot ham and spinach with the sauce.
