Rinse the skate, dry it and cut into even portions. Place the skate in a pot with the stock cube and cold water. Bring to a boil, lower the heat and simmer for 10 to 15 minutes, depending on the thickness of the skate. Take the skate out of the water and remove any remaining skin. Place on a serving plate and keep warm, covered, over a pan of hot water. Melt the butter in a pan and add half the cream. Reduce, stirring, as it thickens, then add the rest of the cream, salt, pepper and capers. When it boils, pour over the skate. Serve with boiled potatoes.
