In a medium bowl, whisk together 1 teaspoon Dijon mustard, 1 teaspoon lemon juice, 2 tablespoons olive oil, and 1/4 teaspoon kosher salt. From 1 head of Boston or butter lettuce, peel off 8 leaves and reserve for another use. Tear the remaining leaves into smaller pieces and add them to the bowl containing the vinaigrette. Add 1/3 cup fresh parsley leaves and 1/3 cup fresh basil leaves. Toss well.