A charred serrano chile is muddled with sugar and fresh mint before being mixed with the margarita trifecta: tequila, orange liqueur, and lime juice.
Place chile directly over a gas flame, or in a dry cast-iron skillet preheated over high and cook, turning a few times, until blackened all over, 3 to 4 minutes. Transfer to a cutting board; let cool completely. Rub a lime wheel around the rims of 2 rocks glasses. Combine salt and sumac on a small plate.
Dip rims of glasses into salt mixture to coat. Halve chile lengthwise; remove stem, ribs, and seeds. Divide chile, sugar, and mint leaves evenly between 2 glasses; gently pound with a muddling stick or the handle end of a thick wooden spoon until sugar dissolves and chile breaks down into tiny pieces. Fill glasses halfway with ice. Divide tequila, liqueur, and lime juice evenly between glasses; stir to combine. Garnish each with a mint sprig and lime wheel, and serve immediately.
To make these even smokier, swap out the tequila for mezcal. The sumac on the rim adds citrus and floral notes, and can be used without salt, if you prefer.