In a small saucepan, heat ½ cup sugar and ½ cup water. Stir until sugar is completely dissolved. Remove from heat and cool.
Add peach slices and lemon juice to a food processor and blend until smooth.
Scoop 1 – 2 tablespoons of the peach puree and a drizzle of simple syrup into a chilled champagne flute.
Fill glass half way with Prosecco and stir lightly to blend before filling glasses.