Put the tequila, pineapple juice, lime juice, agave and rosemary leaves from 1 sprig (no stem) in a mixing glass and lightly muddle the leaves. Add large ice and shake vigorously with a cocktail shaker. Add the prosecco, tumble-roll back and forth 1 time and double-strain over fresh ice into a highball glass. Spear the pineapple chunk with the remaining rosemary sprig for a garnish.
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