Rim copper mule cups or medium glass with lime wedges (reserve limes for garnish).
To small plate, add Tajin seasoning. Dip cup rims in seasoning, turning to evenly coat.
Add ice to cups. Divide mezcal, lime juice and ginger beer among cups; stir to combine.
Garnish with mint and reserved lime wedges.
Tip: For added kick, add 2 slices of fresh jalapeño pepper to each cocktail, if desired.