Put the fruit in a pan with a drop of two of water, and cook slowly until softened. Put through a nylon sieve. Measure the puree and take the ingredients from above. Put the puree into a double saucepan or a bowl over simmering water. Add the butter and sugar and dissolve. Beat the eggs lightly, strain into the mixture and stir until it thickens. Do not allow to get too hot or boil as it could curdle. When thick, pot and store. Eat within 3 months and keep in the fridge.