In a large pitcher, add the raspberries, brown sugar, and finely grated lime zest and muddle gently until the raspberries break down and the sugar fully dissolves, keeping visible texture — this should look juicy and loose, not like a purée.
Lightly tap the mint leaves between your palms to release aroma, add them to the pitcher, and stir once or twice only to perfume the base without bruising the leaves; never muddle mint here.
Stir in the fresh lime juice and white verjus until fully integrated, then taste — the base should already feel sharp, dry, and structured before any carbonation is added.
Fill the pitcher generously with ice, pour in the chilled club soda, and stir very gently once or twice to combine while preserving carbonation.
Pour into ice-filled glasses, garnish with fresh raspberries, mint leaves, and lime slices, and serve immediately while the drink is cold, bright, and lively.
