Name: Sourdough Monster Cookies
Prep time: 45 min
Cook time: 13 min
Total time: 778 min
Ingredients: 350 g All Purpose Flour; 6 g Baking Soda; 6 g Corn Starch; 2 g Salt; 150 g Chocolate Chips; 100 g Peanut Butter Chips; 150 g Mini M&Ms; 100 g Rolled Oats; 100 g Peanut Butter; 100 g Sourdough Starter ((or Sourdough Discard)); 180 g Salted Butter ((melted)); 160 g Brown Sugar; 100 g White Sugar; 2 Eggs; 5 g Vanilla Extract

Sourdough monster cookies are irresistibly nostalgic with a tangy twist. These soft, chewy cookies are loaded with peanut butter flavor, gooey peanut butter chips, melty chocolate, and fun pops of color from mini M&M’s. The sourdough starter (or discard) gives these cookies a subtle tang that will leave everyone craving them.

Large round white plate with sourdough monster cookies sitting on wooden table.

I have so many sourdough cookie recipes with fun flavors. If you enjoy these monster cookies, you will also love these sourdough peanut butter and jelly cookies, sourdough lemon crinkle cookies, and these sourdough strawberries and cream cookies.

Why You'll Love This Recipe!

Nostalgic + a Twist - adding sourdough to this classic cookie creates a lovely tang that adds to the mix-in flavors, making them even better.

Perfect Texture - these cookies are nice and chewy - but still soft - with just enough gooey peanut butter and chocolate bites and perfectly crisp edges.

All the Mix-Ins - every cookie is full of peanut butter chips, chocolate chips, just enough oats for texture, and mini M&M’s to make every bite delicious.

Sourdough monster cookies on wooden table with a cookie with a bite taken out sitting on plate next to a bowl of mini m&ms.

Ingredients

All Purpose Flour
Baking Soda
Corn Starch - most of my cookies include corn starch. It helps with that perfect texture and prevents them from spreading too much.
Salt - I always add just a pinch of salt to cut through the sweetness. I love the flavor it adds, but leave it out if you don't enjoy the contrast.
Chocolate Chips - I prefer chocolate chips, but you can use chocolate chunks if you'd like a more melted chocolate texture. I've used semi sweet chocolate chips.
Peanut Butter Chips - the peanut butter chips give a nice burst of peanut butter flavor in each bite.
Mini M&Ms - besides being fun and colorful, the candy shell gives a little crunch that works beautifully. I've used Mini M&M's, but you can use regular size ones if you prefer.
Rolled Oats - oats add a nice bit of chewiness. Make sure to use traditional rolled oats, not quick oats.
Peanut Butter - use creamy peanut butter for best texture. If using natural peanut butter, make sure to mix it well before adding as the oil can .
Sourdough Starter - you can use either sourdough starter or sourdough discard for this recipe.
Butter - I prefer salted butter, but you can use unsalted if you prefer. Make sure to melt the butter and let it cool a bit, but it should still be warm when you add it.
Sugar - I've used white and brown sugar to keep the insides soft and moist and get crispy edges.
Eggs - use large eggs. My backyard chicken eggs are about 60g each.
Vanilla Extract

How To Make Sourdough Monster Cookies

I've created this recipe based on my no fail soft and chewy sourdough chocolate chip cookies, and added in the mix ins monster cookies are known for. They're absolutely delicious, and a huge hit with my family. Seriously, I had to make so many batches when I wanted to photograph this recipe because they kept disappearing.

Place some of the dry ingredients (flour, baking soda, corn starch, salt, chocolate chips, peanut butter chips and mini M&Ms) into a large mixing bowl and combine. Set this aside.

Dry ingredients mixed in bowl with a spoon for sourdough monster cookies.

Now in a separate bowl, combine sourdough starter, melted butter, brown sugar, white sugar, eggs and vanilla extract. Stir together until they resemble runny caramel.

Wet ingredients for sourdough monster cookies mixed in a bowl with a whisk.

Now pour the wet ingredients into the dry ingredients and stir to form the cookie dough.

Sourdough monster cookie dough mixed together in a bowl.

Cover the bowl with plastic wrap and place into the fridge for 12 to 24 hours.

The next day, when you are ready to bake the cookies, preheat the oven to 165C (330F) and line two cookie sheets with parchment paper.

Use a cookie scoop or large spoon to scoop out balls of dough. I have used 55g dough balls for this recipe (created used a large tablespoon cookie scoop). Place the dough balls onto the prepared baking sheets.

You can add extra mini M&Ms to the top of the cookie dough balls if you want some extra pops of color when baked. This really does create a beautifully colored sourdough cookie.

Sourdough monster cookie dough scooped with a cookie scooper onto baking sheet lined with parchment paper.

Sourdough monster cookie dough in cookie shape on parchment paper lined baking sheet.

Place the cookies into the oven for 12 to 13 minutes at 165C (330F) or until they are golden brown on top but still molten in the centre.

Remove from the oven and allow to cool on the tray for around 10 minutes. The cookies will continue to bake for a few minutes after they are removed from the oven and will firm up as they cool. After 10 minutes, carefully transfer to a wire rack and allow them to cool completely.

sourdough monster cookies on a wire cooling rack with a bite of one cookie taken out.

Kate's Recipe Tip

To make sure you get the pops of color these cookies are renowned for, add some mini M&Ms to the cookie dough balls before baking. You'll be so glad you did when you see the finished product!

How To Store + Freeze

These cookies stay fresh for about 3 to 4 days when stored in an airtight container. I like keeping mine in a glass jar because it keeps them soft and chewy. I’d skip plastic containers if you want to keep that perfect texture.

Freeze them on a cookie sheet first, then transfer them to a ziploc bag. That way you can pull out just a few to toss in lunchboxes or enjoy as a quick treat. They will stay fresh for up to 3 months and thaw beautifully.

If you want fresh-baked cookies anytime, you can also freeze the dough balls. Scoop the dough into balls, and snap freeze them on a tray, then store the frozen balls in a ziploc bag. When you’re ready, just pop them on a baking sheet, let them soften a bit, and bake as usual. It’s such an easy way to have warm cookies whenever you want.