In a high-speed blender, combine the sliced strawberries with 1 cup of water. Blend until the mixture is completely smooth. Once blended, strain this strawberry mixture through a fine-mesh sieve into a large pitcher to remove any seeds and pulp. Use a spatula to help push the liquid through for maximum yield.
In a small saucepan, bring 1 cup of water to a vigorous boil. Once boiling, remove the saucepan from heat and immediately add the granulated sugar. Stir continuously until the sugar is completely dissolved to form a simple syrup. Set this aside to cool for a few minutes.
Pour the freshly squeezed lemon juice into the pitcher containing the strawberry puree. Next, add the cooled simple syrup and stir well to combine all the flavors harmoniously.
Take the basil leaves, tearing them into smaller pieces to release their essential oils, and add them to the pitcher. Allow the mixture to infuse for about 10-15 minutes.
Once infused, add the remaining 3 cups of cold water to the pitcher and stir thoroughly. Taste your lemonade and adjust the sweetness or acidity by incorporating more sugar or lemon juice as necessary until you achieve your desired flavor profile.
To serve, fill glasses with ice cubes and pour the refreshing strawberry basil lemonade over the ice. Garnish each glass with a slice of lemon and a sprig of basil.
Notes
Adjust sweetness to your preference by adding more sugar or lemon juice.