For the pepper-infused tequila: Drop the jalapeno into the tequila and let it infuse for 4 to 5 hours. Discard (or bravely eat) the jalapeno.
For the mango puree: Peel the mango and cut the flesh away from the pit. Add the mango to a blender with 1 tablespoon water and blend until smooth.
For the cocktail: Put 2 ounces of the pepper-infused tequila (reserve the rest for another use), 1 ounce of the mango puree, the agave syrup, lime juice and 3 to 4 ice cubes in a blender and blend until smooth. Pour into an up glass and garnish with a ring of thinly sliced jalapeno. Assume a poker face.