Bring to a boil, stirring to dissolve sugar completely.
Simmer for 1 minute longer.
Remove from heat.
Let basil steep in the syrup for 30 minutes, then remove.
Let cool to room temperature.
Store in an air-tight container in the fridge for about a week.
Notes
If the basil flavor still isn't strong enough for you after making this simple syrup, muddle a few extra basil leaves directly to your cocktail.
This same base recipe can create different kinds of herb simple syrups. Swap out the basil for thyme, mint or rosemary.
If you are worried about any small pieces of leaves in your syrup, you can use a fine strainer to get them out before putting it in your storage container.
This recipe is easy to scale up and because it needs to be made ahead of time is great for a party bar!