Smoutebollen, oliebollen or Belgian donuts

A real treat usually enjoyed at the fairground attraction now easily repeated at home. recipe: flour 450gr / 16oz milk 180ml / 6 fl oz sparkling water 180ml / 6fl oz 3 whole eggs fresh yeast 37.5gr / 1.3oz or dry yeast 19gr / 0.65oz (4tsp) 2 x 1 tablespoon white sugar vanilla essence pinch of salt