Waldorf Salad

Ingredients

• 4 red-skinned apples, diced
• 1/2 cup chopped walnuts
• 1 cup chopped celery
• 1/2 cup purple grapes, sliced in half
• 1/3 cup milk kefir
• 1/2 cup sour cream
• 2 tablespoons lemon juice
• sea salt and pepper to taste
• head of butter lettuce leaves for serving