In a small bowl, sprinkle the yeast over the lukewarm milk. Stir briefly to combine and allow to sit at room temperature until frothy, about 10 minutes.
In a large bowl, whisk together the flour, sugar, vanilla sugar, and salt.
Stir in the egg yolks, milk with frothy yeast, and butter. Gently mix in the Prosecco just until no lumps remain.
In a medium bowl, beat the egg whites until stiff peaks form. Lightly fold into the batter until no streaks remain.
Cover the bowl and let sit at room temperature until puffed and bubbly, 30 minutes to 1 hour.
Set waffle iron to high heat.
Grease the heated waffle iron with melted butter.
Spread the batter over the prepared waffle iron, about 1/3 cup (80 milliliters) per waffle. Heat until waffle is golden and crisp on outside. Repeat with remaining batter.
Serve the waffles warm with the Prosecco-soaked strawberries, shaved white chocolate, edible flowers,and honey/syrup if desired.