Pour some cold water and ice cubes into a bowl.
Mix together the cold fruit purée with the Promochi and sugar. Heat up the mixture and whisk until it boils – Make sure you pay attention, as this mixture is liable to stick to the bottom of your pan. Take off the heat, add the cubed butter and whisk until you obtain a smooth, homogeneous texture.
Leave to cool briefly and put the mixture in a piping bag with your preferred nozzle, depending on the shape you want your gnocchi to be.
Hold the piping bag over the bowl of ice water, squeeze and use a knife to cut the gnocchi to your preferred size as the mixture comes out of the nozzle.
Leave to set in the ice water for a few moments, then serve immediately.