Add all the ingredients into a shaker with ice and shake.
Fine-strain over fresh ice in a rocks glass.
Garnish with a mint sprig.
*Stone-ground yerba mate syrup: Add 1/4 cup stone-ground yerba mate, 4 cups granulated sugar and 4 cups hot water into a saucepan over medium heat, and stir for about 10 minutes until evenly saturated and sugar is dissolved. Let cool.