For the Ancho-Arbol Syrup, mix all ingredients in small saucepan. Bring to boil. Reduce heat to medium-low; simmer 5 minutes. Remove from heat. Let stand 2 hours. Strain through double layer of cheesecloth or coffee filters. Cover and refrigerate until well chilled. (This makes enough syrup for 4 cocktails)
For each cocktail, place 2 lime wedges, 2 sprigs mint and 1 sprig cilantro in cocktail shaker. Muddle the lime with a muddler or wooden spoon to release the lime juice. Fill cocktail shaker with ice. Add 1/4 cup each gin and Ancho-Arbol Syrup; mix well. Shake until well mixed and chilled. Strain into tall ice-filled beverage glass. Top each glass with 1/2 cup club soda. Repeat with remaining ingredients to make 4 cocktails.