For the dressing:

1 tablespoon fresh lemon juice
1 tablespoon red wine vinegar, or more to taste
2 teaspoons Dijon mustard
1 clove garlic, minced
Salt and freshly ground black pepper
1/4 cup extra-virgin olive oil
1 to 2 anchovy fillets (optional), rinsed, blotted dry, and finely chopped
1 tablespoon brined capers, drained
12 fresh basil leaves, thinly slivered, plus 4 to 6 small sprigs for garnish