Muddle strawberries, sugar, lemon juice and elderflower liqueur (optional) in a pitcher until fruits break down and sugar has dissolved.
Add one bottle of the Belvoir Elderflower Lemonade (this can be found on Amazon or in specialty grocery stores, but a simple lemonade will do here as well).
Fill glasses with ice a little more than halfway. Pour the strawberry beverage into each glass, leaving room on top. Top off with prosecco (optional).
Garnish with a fresh strawberry, mint and chamomile flowers.