Preheat the oven to 180C/360F/Gas 4. Lightl grease a baking tray with butter.
For the choux pastry, place the butter and water into a pan over a medium heat until the butter has melted.
Remove the pan from the heat, add the flour and mix well with a wooden spoon until the mixture resembles a paste.
Add the eggs, one at a time, mixing until completely combined before adding the next egg.
Transfer the dough into a piping bag, then pipe small blobs of dough onto the greased baking tray.
Bake in the oven for 15-20 minutes, or until dry and hollow. As soon as they are cooked, use the handle of a teaspoon to poke a small hole into the base of each profiterole to allow any steam to escape. Set aside to cool.
For the filing, place the whipped cream into a bowl and fold in the vanilla essence and icing sugar, to taste.
Spoon the cream mixture into a clean piping bag and fill each profiterole with it.
Spread a little melted dark chocolate onto a large plate or cake stand. Arrange a layer of profiteroles onto it.
Place more chocolate on top of each profiterole, then add a second layer of profiteroles, slightly smaller in diameter than the first layer.
Top the second layer of profiteroles with melted white chocolate, then add another layer of profiteroles.
Repeat the process with the remaining profiteroles until the layers resemble a pyramid and all of the profiteroles have been used.
To serve, drizzle over any remaining melted chocolate and present at the table.