Toss 2 cups cubed raisin-walnut bread with 2 tablespoons melted butter. Bake at 400 degrees F until crisp, 12 to 15 minutes. Puree 1/4 cup each mayonnaise, sour cream, buttermilk, sliced scallions, chopped dill and chopped mint, and 1/4 teaspoon kosher salt in a blender. Toss 2 chopped romaine hearts with the dressing, 1/2 cup candied pecans and the croutons. Season with salt and pepper.