Shake all ingredients in a shaker with ice. Pour through a strainer into a lowball glass with a large-format ice cube. Garnish with a thin slice of jalapeño and serve.
Notes
If you prefer less heat, reduce the cayenne pepper.We use a 2:1 simple syrup for this recipe. You can make your own at home by combining two cups of sugar with 1 cup of water over medium heat and simmer for about 10 minutes until all the sugar has dissolved. Then remove from the heat and cool before transferring to an air tight container or using in a cocktail. You can store the simple syrup in the fridge for up to 6 months.