1Combine milk, oats, yogurt, honey, peanut butter, flaxseed meal, vanilla extract, and salt in the bowl of a stand mixer. Mix on low speed until oats are soft, about 30 minutes.
2Pour mixture into 10 half-pint jars. Sprinkle 2 tablespoons cranberries and 2 tablespoons walnuts into each jar. Refrigerate before serving, 1 to 10 days.