I don't always have buttermilk on hand, so, if you're like me and don't feel buying some, use regular milk instead (whole milk if you have it, or 2%) and leave out the baking soda. For an even more indulgent, doughnut-like puff: Make an extra two tablespoons of the browned butter and roll the whole puff in it and the cinnamon sugar. (I usually have enough cinnamon sugar to fully roll the puffs.) Do ahead: Puffs are best within hours after they are baked. They can be made it advance and stored in a freezer bag until needed, too. Simply spread them out on a baking tray and reheat them until warm in the oven.