Combine the berries, sugar, water, and sliced peppers in a medium-sized saucepan and stir.
Cook the mixture over medium heat, bringing it to a simmer. Once the berries are slightly softened and cooked, use a potato masher to crush the berries, creating a thin jam.
Continue to cook over medium heat for 10 to 15 minutes, stirring occasionally, until the syrup thickens slightly.
Once cooked, carefully pour the hot syrup into a fine-mesh strainer set up over a large bowl. Use a spatula to press as much juice and pulp from the berries as possible, leaving behind just the seeds.
Stir the syrup, then set into the refrigerator or freezer to cool.
Making Blackberry Margarita:
Make sure to wash your limes first! Fill a large bowl with cold water, add a few tablespoons of baking soda, and let the limes sit in this solution for 10 to 15 minutes before rinsing clean.
Slice the limes in half, then use a citrus press to squeeze out the juice. Strain the juice through a fine-mesh strainer to remove any pulp; if desired.
Pour the chilled blackberry syrup into a large pitcher or measuring cup. Add the freshly squeezed lime juice, tequila, triple sec, and mix well.
Set the margarita mix into the refrigerator to chill for a few hours, or overnight.
Serving & Garnishing:
For the sugared rim – combine ½ cup sugar with a few teaspoons of sea salt in a shallow bowl and set aside until ready to use.
When you’re ready to enjoy – moisten the rim of your glass (any type will work) with a lime wedge, then dip into the sugar and salt mixture.
For 2 cocktails: fill a cocktail shaker with 1 cup ice and add 1 cup margarita mix. Shake vigorously for a few minutes, then pour into the prepared glasses. Serve it on the rocks (with extra ice in the glass), if desired.
Garnish the glasses with lime wedges, or use a cocktail skewer with berries, sliced peppers, and lime pieces.
Store the blackberry margarita mix in the refrigerator for up to 1 week. You can also freeze the mix in freezer-friendly containers.
Recipe Variations:
Sweeter Version: for a sweeter margarita, increase the amount of sugar added to the syrup from ¾ cup up to 1 ½ cups. Alternatively, add agave syrup or honey to the cocktail shaker for individual drinks.
Spicier Version: love a little extra heat? Add a few extra chilis to the blackberry syrup. You can also add sliced chilis to the margarita mix and let it stand overnight.
Blender Version: if you enjoy a blended margarita, add 1 cup ice and 1 cup margarita mix to a blender and pulse until the mixture is slushy and uniform. Enjoy immediately.