Cream of tartar, or potassium acid tartrate if you want to get chemical about it, is a fine, white powder made by purifying and grinding the crystals that form inside wine barrels during the wine-making process It’s also an ingredient in baking powder. You can find it in the spice section of the grocery store.
Cream of tartar has many cooking uses. It’s most commonly used in whipping egg whites; a pinch will give whites increased volume and make them more stable so they’re less likely to fall. It keeps sugar from crystallizing so it’s often used to keeps candies, frostings and meringues smooth and shiny. In baked goods, cream of tartar is used as a leavener, to give cakes, muffins and cookies their rise. It has a tinny, metallic taste that’s most noticeable in Snickerdoodle cookies. A tiny pinch added to water also helps vegetables maintain their color when they’re blanched.
Speaking of snickerdoodles (see what I did there?), my recipe for Lemon Cardamom Snickerdoodles is one of my all-time favorite cookies (besides Chocolate Chip, of course). I first had a regular snickerdoodle when a volunteer dropped off a batch at the campaign office I was working on. (I worked in politics before I became a chef, but that’s another story.) I was hesitant to eat from a stranger’s kitchen, but cookies. One bite and I was hooked. The tinny taste of the cream of tartar was intriguing but not overpowering. I tracked the nice volunteer down, got the recipe and my snickerdoodle experimentation began.