Put the butter into a heavy saucepan with the water and heat over a medium heat for about 10 minutes or until the butter melts. Bring to a boil but take care not to burn the butter.
Take the saucepan off the heat and add the sieve plain flour. Stir vigorously with a wooden spoon until the mixture forms a soft ball. This should take around 3 minutes.
Leave to cool slightly then gradually add the eggs, beating well between each addition, to form a smooth, shiny paste.
Butter a baking tray and sprinkle with water. Put 12 tablespoonfuls of pastry on the tray. Bake in a preheated oven at 220°C/gas mark 7 for 10 minutes, then reduce the heat to 190°C/gas mark 5 and bake for 20 minutes. Split each profiterole in half and cool on a rack.
For the wicked chocolate icing, gently melt the chocolate with the double cream in a bowl over a pan of simmering water, stirring until smooth and shiny (taking care not to let it get too hot).
Sandwich the profiteroles together with the whipped cream, place on individual plates, and drizzle with the chocolate icing.