Remove stems from strawberries and chop as finely as possible. Add to a cocktail shaker.
Cut limes and squeeze fresh lime juice into cocktail shaker with chopped strawberries.
Break up basil into small bits and add to cocktail shaker. Then, take a cocktail muddler and muddle ingredients together to form a purée.
Add tequila and ice to cocktail shaker and shake until well-mixed.
If desired, wet the outer rim of your glass with lime juice and coat in sugar. Then, using a cocktail strainer, pour margarita over ice and top with strawberry slices and a sprig of basil.