For the Ancho-infused Rum:
Remove stems from chilies, reserving seeds. Break chilies into small pieces and add them, along with the seeds to the rum. Infuse for 2 hours and fine strain.
For the Scarlet Fever:
In a cocktail shaker, combine El Dorado rum, ½ ounce Ancho-infused Rum, pineapple juice, lime juice, and cinnamon syrup. Add ice, shake, and strain into a glass filled with cobble ice.