How to Make It
Place 4 oz. tequila and 1 small serrano chile, halved lengthwise, in a small bowl or cup. Let stand 1 hour. Strain mixture through a fine-mesh sieve over a cup; discard solids. Blend 12 oz. fresh blackberries, 1 cup fresh orange juice, 1/2 cup fresh lime juice, 2 Tbsp. agave nectar, and a dash of salt until smooth. Strain mixture into a pitcher; discard solids. Stir in tequila. Divide mixture among 4 ice-filled glasses. Garnish with additional blackberries and a chile, if desired.