- In a cocktail shaker, add the ¼ cup loosely packed basil leaves and gently muddle them to release the basil essence. 
- Add enough ice to fill the shaker or cocktail mixing glass halfway. 
- Pour the limoncello and vodka into the shaker or mixing glass and shake or stir well. 
- Strain the chilled mixture into a coupe glass or a similar glass, filling it halfway.  
- Top with prosecco or club soda.  
- Garnish glasses with 3 small basil leaves and a thin slice of lemon. 
- Serve immediately.