In a medium saucepan, combine the sugar, 1 cup of water, and basil leaves. Heat over medium heat, stirring until the sugar dissolves completely. Remove from heat and let the basil steep for 5 minutes, then strain out the leaves and set the syrup aside to cool.
Add the strawberries to a blender and blend until completely smooth. For a smoother lemonade, strain the strawberry puree through a fine mesh strainer to remove seeds.
In a large pitcher, combine the cooled basil syrup, fresh lemon juice, and strawberry puree. Stir well to combine.
Add 3 to 4 cups of cold water, tasting as you go, until the lemonade reaches your preferred strength.
Serve over ice and garnish with fresh basil leaves or sliced strawberries if desired.
Notes
Tips for the Best Strawberry Basil Lemonade
Use ripe strawberries for the best flavor. The sweeter the berries, the better your lemonade will taste. Always use freshly squeezed lemon juice instead of bottled juice, as it makes a noticeable difference. Let the basil steep briefly rather than boiling it too long to avoid bitterness. Taste as you go when adding water so you can control how strong or diluted the lemonade becomes.
Variations and Substitutions
For a lighter version, substitute honey or agave syrup for sugar. If you prefer sparkling drinks, replace half of the cold water with sparkling water just before serving. You can swap basil for mint if you want a more classic flavor. For an adult version, add vodka, gin, or white rum to individual glasses. Frozen strawberries work well when fresh ones are out of season and also help keep the drink extra cold.