In a small sauce pan over low heat, combine honey, water, and serrano. Simmer for about 5 minutes, until syrupy. Let cool.
In a blender, combine honey syrup (with serranos), mango, 1/2 cup water, and lime juice. Blend until completely smooth.
For each drink, add 1/4 the mango mixture and 2 oz tequila to a cocktail shaker filled with ice. Strain into a chilled margarita glass. May double this to shake two drinks at a time.
Garnish with serrano slices and enjoy!