Williams Brewster Punch

These quantities make a communal punch batch using two bottles of Champagne.

Combine the pear eau de vie, rosemary syrup, and freshly squeezed lemon juice in a punch bowl over a large block of ice.

Stir in the brut Champagne and soda water just before serving.

Garnish with sprigs of rosemary and twists of grapefruit peel.