To make heavy cream, take 1 cup of whole milk and add 2 tablespoons of cornstarch and let sit to thicken and then use in your recipe.

To make buttermilk, take regular whole milk (or heavy cream), and add 1 tablespoon of vinegar (or 1 tablespoon of fresh lemon juice). Let the milk mixture stand for 10-15 minutes and you will have a perfect buttermilk substitute. Another substitute is Greek yogurt thinned with whole milk or water to the consistency of heavy cream