Sourdough cookies, like last week’s sourdough cracker recipe, have two goals: capture some sour flavor and use your starter. Sourdough’s leavening power doesn’t take charge: you’re still relying on baking soda, baking powder, or both to create the cookies’ shape. That puts them in the same category as Sourdough Pancakes, Sourdough Waffles, and quick breads.

But unlike those baked goods, putting sourdough starter in cookies bumps up against some problems. Most cookies have a low hydration level—they have little or no added liquid. The “wet” ingredients they do have usually contain fats, proteins, and other elements that balance the cookie recipe. This week, I focus on things I’ve learned about baking cookies with sourdough and the best recipes to use with your starter.

Converting Recipes

I have plenty of tried-and-true cookie recipes, so I started by putting sourdough in my favorites. The general rule when converting from yeast to sourdough relies on the hydration level of your starter. I keep mine at 100% hydration, so I replace equal parts flour and water by weight, plus the yeast, with starter. This can work with quick breads too—if they use water.

For recipes that don’t use water, like all of my favorite cookie recipes, you need to swap out something else. The flour part is easy, because you can just cut back the recipe’s flour. The liquid part leaves you with some dilemmas: do you cut back the butter, the eggs, a liquid sweetener, or some other ingredient?

Replacing an Ingredient

The easiest cookies to convert to sourdough are cakey cookies that feature an added ingredient. The obvious choice for my first sourdough cookie conversion was a recipe that used sour cream. The sour cream acts as an acidic ingredient that reacts with the recipe’s baking soda, giving the cookies their loft. It also has a thicker texture than water, so I simply replaced the recipe’s sour cream with sourdough starter.

The sourdough cookies made with active starter actually had less tang than the sour cream version. Even when I let the dough sit in the refrigerator for several days, I only tasted a slight change in the flavor. So if you’re looking for a less sour cookie, or if you just want to use your active starter, this might be your solution. A dormant, unfed starter gives more tang, but I have yet to match the flavor of my Homemade Sour Cream.

Here’s my solution for making these cakey cookies with sourdough, plus another recipe to try with a similar treatment:

• Salted Chocolate Chip Cookies. Replace the sour cream with 3/4 cup (180 grams) 100% hydration sourdough starter, adding the starter with the butter and sugar instead of later in the process. Instead of freezing the dough, chill it for at least 1 hour in the refrigerator.
• Pumpkin–Chocolate Cookies. Replace up to 3/4 cup (180 grams) of the pumpkin with 100% hydration sourdough starter, adding it before the pumpkin.

Finding a Balance

Less cakey cookies require more of a balancing act, because if you want to reduce the “wet” ingredients, you have to drop some fats, proteins, or both.

I started testing these variations with my old family favorite: snickerdoodles. I went big with my first attempt, cutting back on the eggs and butter, as well as flour, so that I could mix in a full cup (240 grams) of starter. The flavor was good, but the cookies spread flat and crisp, even after I left the dough in the refrigerator for a couple of days. So I tried swapping in half as much starter. The texture improved, letting the cookies retain much of their shape.

Here’s my solution for converting snickerdoodles to sourdough, plus another recipe to try with a similar treatment:

• Snickerdoodles. Cut back to 1 egg and 2-1/4 cups of flour, and then add 1/2 cup (120 grams) 100% hydration sourdough starter; mix the starter into the butter, coconut oil, and sugar.
• Freshly Ground Peanut Butter Cookies. Cut back to 6 tablespoons of milk and 2 cups of flour, and then add 1/2 cup (120 grams) 100% hydration sourdough starter; mix the starter into the butter and peanut butter. Instead of freezing the dough, chill it for at least 1 hour in the refrigerator.

Twice as Tasty

Now that you understand the process, I encourage you to apply the technique to your favorite cookie recipes. Unless there’s an obvious 1:1 replacement, like sour cream, I recommend starting with a small amount of starter, say 1/4–1/2 cup (60–120 grams), to see how the starter affects the shape and texture. If you use a 100% hydration starter, you can cut back the flour and a liquid in equal parts by weight. If you keep your starter at a lower or higher hydration, you’ll need to adjust the flour and liquid to match.

Weight versus volume can seem complex when adding an ingredient usually measured by weight (starter) to a recipe usually made with volume measurements (cookies). But it’s really the opposite. Measuring sourdough starter by weight is the lazy solution: Set the bowl on the scale and pour in the starter, avoiding the sticky mess it makes of measuring cups and spatulas. You can then add the rest of your ingredients using the volumes written in the recipe.

Like what you’ve learned but don’t have a sourdough starter? Now’s your chance! The 4th Annual Sourdough Giveaway runs through January 31, 2021. Learn how to get your free sourdough starter here.