Line the base of a Swiss roll pan with parchment paper. Brush the base and sides of the pan with melted butter and layer some baking paper then spray some oil.
In a large bowl, whisk together the eggs and sugar until light and fluffy, then add the water and vanilla extract.
Fold the flour into the egg mixture, a little at a time.
Gently pour the mixture into the prepared pan and bake in the oven for 12-15 minutes.
Spread out a piece of baking paper on a work surface and sprinkle evenly with sugar.
Gently invert the Swiss roll pan onto the sugared baking paper and carefully remove the pan and parchment paper from the bottom of the cake.
Place a slightly damp, clean kitchen towel over the cake while it cools to keep it moist.
Hull and slice some strawberries, then add to a blender or food processor. Process until blended into a puree. You will need 4 tablespoons puree, so add more sliced strawberries if needed.
Whip the heavy cream with a hand mixer until it begins to form soft peaks. Mix in the sugar until stiff peaks begin to form, then add the 4 tbsp pureed strawberries. Spread the mixture over the sponge cake.
With the longest side facing you, gently roll up the Swiss roll away from you.
If you like to decorate with chocolate, melt some chocolate chips then drizzle the melted chocolate over the cake with a fork, a teaspoon or a piping bag.