In a medium saucepan, combine water, chopped chiles, and lime zest (not the juice), stirring to combine. Bring mixture to a simmer over medium heat and let simmer for 4 minutes. Remove from the heat and add lime juice and agave nectar, stirring until the nectar dissolves.

Let the syrup cool then pour through a fine-mesh strainer into a clean jar or pitcher. Discard solids.

To make an Ancho Chilie Margarita, add 2 oz. golden tequila to a shaker with ice then pour in ancho lime syrup and lime juice to taste (I did about 1.5 oz. syrup and juice from 1/2 a lime). Shake until thoroughly chilled. Strain into a glass with ice. Top off with sparkling water and garnish with a lime wedge.