I Made a Sourdough Discard Flax Egg Because Why Not?

You may have replaced an egg with a flax egg but have you tried a sourdough discard flax egg?

Over the years, I have made several attempts to add sourdough starter or discard to cookies, always with mediocre results. Then I wondered if I could sneak a bit of discard into a recipe via a sourdough discard flax egg. It worked and I’m so excited. One more use for discard! Plus cookies!

First things first. How to make a simple flax egg

A flax egg makes an excellent egg replacer in cookies. It will not work in cakes or, unsurprisingly, soufflés or omelets. I have not had blog-worthy results in quick breads. But for many cookie recipes, I actually reach for flax eggs first. Sometimes when people taste a recipe you’ve tweaked—”Try this! I omitted all the sugar!”—they can tell. No one I’ve fed cookies to with flax eggs in them can.

If you haven’t tried baking with a flax egg, to make one, combine 1 tablespoon of ground golden or brown flaxseed meal with 2½ tablespoons of water. As the egg replacer sits for 10 or 15 minutes, it coagulates into a gelatinous consistency that helps bind ingredients.

While the flax egg coagulates, measure the other ingredients, prep a baking sheet (if necessary), preheat the oven and so on. By the time the flax egg has reached the proper consistency, you’ll have reached (or nearly reached) the step at which the recipe instructs you to mix in the egg. You’ll mix in your egg replacer.


Even if you aren’t vegan, you’ve no doubt run out of eggs in the middle of baking cookies and have searched for a replacement. Or perhaps the store has run out of eggs! Or maybe you just like saving money. The price of eggs increased by 49 percent in the US in 2022. If you can find any.

Low stock of eggs at the grocery store (January 2023)

Keep a bit of flaxseed meal on hand (or flaxseeds if you have a grinder) and you can bake all the cookies you want.

35 ranger cookies with oats and raisins are arranged on a silver cooling rack that sits on a wooden board
Ranger cookies made with a flax egg

Sourdough discard flax egg

Flax meal eggs are not new. If you search online, dozens of recipes for them and articles about them will pop up. But sourdough discard flax eggs? Because discard contains only flour and water, I wondered if I could make a sourdough discard flax egg with it, swap that for the egg in a cookie recipe and compensate for the flour present in the discard by reducing the flour called for in the original cookie recipe. Turns out, I can!

To replace one egg in a cookie recipe that calls for flour, combine:

  • 3 tablespoons sourdough discard (47 grams)
  • 1 tablespoon flaxseed meal (8 grams)

1. Let the mixture sit for 10 to 15 minutes to thicken up. It will become quite stiff.

2. Adjust the original cookie recipe by removing 3 tablespoons of flour for each sourdough discard flax egg added.

3. Mix the sourdough discard flax egg into the ingredients at the recipe’s chicken-egg-adding step.

Note bene!

  1. Substitute a sourdough discard flax egg in recipes that call for flour. Do not replace eggs in coconut macaroons or meringues, for example, or in recipes that call for a copious number of eggs. Look for cookie recipes that call for one or two eggs.
  2. Use sourdough discard at 100 percent hydration. This simply means your sourdough starter’s feedings contain equal amounts of flour and water by weight (not volume). For example, I feed my starter 40 grams of water and 40 grams of flour at each feeding.
  3. Use discard that you constantly replenish. You may add to it one day when you feed your starter and take some out a couple of days later to make pizza. You don’t want to use discard that has sat in the refrigerator for a couple of months untouched. Go here for FAQs on discard.
  4. You may have to do a little bit of tweaking and add some extra fat to your recipe. If the dough is crumbly, add one or two more tablespoons of butter.

The sourdough discard flax egg in the bowl below looks quite wet because I added the vanilla on top as I made ranger cookie dough. As you can see, the “egg” becomes very thick!

A stainless steel bowl of creamed butter and sugar and a beige blob that is a sourdough discard flax egg
The “egg” becomes thick and stiff
Peanut butter cookies made with a sourdough discard flax egg cool on a silver baking sheet.
Peanut butter cookies made with sourdough discard flax eggs

So far, I’ve made peanut butter cookies, ranger cookies and oatmeal cookies using a sourdough discard flax egg—all delicious!

A stainless steel bowl or ranger cookie dough sits on a table, with jars of ingredients in the background
Ranger cookie dough with a sourdough discard flax egg

Ferment the cookie dough if desired

To ferment the dough, let it sit on the counter at room temperature for up to six hours. The dough contains a small amount of sourdough discard—3 tablespoons per egg replaced. Such a small amount of inactive sourdough discard contains way fewer microbes than a lively starter ready to bake sourdough bread.

But if the dough sits and ferments, those good yet tired microbes in the sourdough discard will chow down on their new food source—carbohydrates in the flour and sugar—and multiply, boosting the live cultures in the dough. Not that cookies are probiotic health food! But fermenting the dough aids in digestion.

When fermenting the dough, add any dried fruit just before baking

If you add dried fruit such as raisins to the dough and let the mixture sit on the counter to ferment, the dried fruit will draw moisture from the dough, leaving the dough dry and the fruit plumped up, throwing off the dough’s makeup. Wait to add dried fruit to dough after it has fermented on the counter.

Stay tuned for cookie recipes containing the sourdough discard flax egg!

Check out my award-winning cookbook!

My book won silver for single-subject cookbooks at the Taste Canada awards! It also won a second-place Gourmand cookbook award in the category of food waste. And it was shortlisted for an award from the International Association of Culinary Professionals.

Learn more about my book here.

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6 Replies to “I Made a Sourdough Discard Flax Egg Because Why Not?”

  1. Wonderful discovery, Anne-Marie!

    1. Thank you very much! I wasn’t sure if it would work but it works so well!

      1. You’re welcome. In a bit of synchronicity, a friend of mine made gingerbread cookies with a mix and the water-flax egg not long ago and I was surprised at how good the cookies tasted.

  2. Congratulations on the success of your cookbook, Anne-Marie I love my copy…Not having ever used flax eggs and unless the chooks or the ducks stop laying I’m unlikely too but it is a very informative post and one I will be sharing in my next months Green Kitchen for anyone who does use flax eggs 🙂 Thank you for sharing 🙂

    1. Thank you very much Carol. Oh I would love to have chickens or ducks! One day! Thank you for offering to share the post 🙂

      1. My pleasure, Anne-Marie 🙂

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