Start by chilling a champagne flute.
To make the peach purée, cut the peach into slices, removing the pit, but leaving the peel.
Blend the peach slices and strain.
Refrigerate for up to one hour (fresh purée is best for this cocktail).
When you are ready to make the drink, pour the peach purée into the flute followed by the Prosecco.
Carefully stir until combined.