Pre-chill a Collins glass by filling it with ice water and setting aside.
Prepare a lime wedge garnish.
Combine 45ml reposado tequila, 15ml crème de cassis, and 22.5ml fresh lime juice in a cocktail shaker.
Add ice and shake vigorously for 10–12 seconds.
Discard the ice water from the Collins glass and fill it with fresh ice.
Strain the shaken mixture into the prepared glass.
Top with 60ml ginger beer and briefly stir once to integrate.
Garnish with the lime wedge and serve immediately.
The El Diablo dates back at least to Trader Vic's 1946 book, making it one of the earliest known tequila cocktails to gain widespread recognition in the United States. Using a reposado rather than blanco tequila adds a subtle oak depth that anchors the berry and ginger flavors beautifully.
My Bar Shelf reads your shelf and shows you every cocktail you can make from what you already own, including El Diablo Cocktail.