Copycat Costco Chocolate Muffin Recipe

My version of the iconic Costco Chocolate Muffin is so easy to make with simple pantry ingredients! Start with bloomed cocoa powder, then add some sour cream for extra moisture and plenty of melty chocolate chips. You’ll get giant, bakery-style results every time that you won’t be able to resist!!

Costco Chocolate Muffin

I’ll be the first to say it… I love Costco!! Their selection is ENORMOUS, and with a bunch of recipes to test each and every week, we go through a lot of ingredients in our house… and fast!

Every couple of weeks or so before I go I ask everyone in the house if they want anything specific. Both my husband and daughter always request something sweet.

We are all obsessed with the bakery section. But one treat that stands out amongst the rest is definitely the famous Costco chocolate muffin! 

My version is just as good (if not better, ahem). These muffins are rich, indulgent in the best way, and totally bursting with deep chocolate flavor. 

And, they’re super easy to make with some key tips and tricks!

This Costco double chocolate muffin recipe is just the latest in my growing collection! Try my blueberry muffins, corn muffins, pumpkin streusel muffins, and apple cinnamon muffins next. 

Ingredient Notes and Substitutions

• All-Purpose Flour – Regular AP flour works well for these Costco chocolate muffins. Make sure to measure correctly by spooning and leveling to prevent dry and crumbly results! 
  
• Unsweetened Cocoa Powder – Provides that yummy, deep chocolate flavor. Natural, unsweetened cocoa powder works best. 

Dutch-processed cocoa could also be used, but understand it may alter the flavor a bit.

• Granulated Sugar – For sweetness of course! Sugar also surprisingly adds moisture. In fact, it’s considered a wet ingredient!
  
• Baking Soda & Baking Powder – Both are needed to help the muffins rise. If yours has been sitting in the cupboard for a while, double-check it’s not expired.
  
• Vegetable Oil – Also keeps the muffins moist. Melted butter is a decent sub, but it will give you a denser texture.
  
• Eggs – Binds everything together, and the extra yolk incorporates even more richness. 
  
• Hot Water – Needed to “bloom” the cocoa powder. Not only does this enhance the chocolate flavor, but it also makes it easier to dissolve into the Costco chocolate muffin batter.
  
• Vanilla Extract – Adds to the overall sweetness.
  
• Sour Cream – My secret ingredient for extra moist and rich muffins! Don’t substitute with low-fat sour cream — it’s just not the same.

If you do need an alternative, Greek yogurt is your best bet.

• Chocolate Chips – I like semi-sweet chips like in the chocolate muffins at Costco, but you could also try milk chocolate, dark chocolate, or even white chocolate for variety. 

Whatever you choose, make sure they’re high-quality for the best melt.

Tips and Tricks to Make Perfect Costco Chocolate Muffins

• Don’t skip the blooming step!

It bears mentioning twice! 

Combining the cocoa powder with hot water so it “blooms” makes it taste even more chocolaty. It also prevents any dry, powdery lumps from messing with the batter. 

Let it cool slightly before adding it to the wet ingredients so you don’t end up with scrambled eggs.

• Use room temperature ingredients.

Bring the eggs and sour cream to room temperature first for the best texture. 

Eggs that are too cold can cause the Costco chocolate muffin batter to seize, and cold sour cream won’t incorporate as smoothly. 

All of the above could cause the muffins to go flat! 

• Fill the muffin cups generously.

For big, bakery-style muffins, fill your jumbo muffin cups about ¾ full.

This helps create a high, domed top just like the chocolate muffins at Costco.

• Check for doneness early.

I usually start around the 25-minute mark to ensure nothing has burned.

You’ll know they’re done when a toothpick comes out clean with a few moist crumbs but no wet batter.

If you leave them in for too long, the muffins will come out too dry, so be careful!

Prep Ahead

• Bring the sour cream and eggs to room temperature
• Measure out and divide the cocoa powder and chocolate chips

Kitchen Tools You Will Need

• Mixing Bowls – I like to have a variety of sizes on hand, and this set has them all.
• Whisk – These have held up for over 10 years and are still as good as the day I bought them. With 3 sizes, there is a whisk for every job!
• A sturdy Silicone Spatula can be used for scraping, stirring, and smoothing and is easy to clean too! 
• Jumbo Muffin Tin & Liners
• Cooling Racks – Cool a large batch of treats without taking up a lot of counter space.

How to Get Bakery-Style Muffins

There are a couple of easy tips and tricks you can use to get results that are exactly like the chocolate muffins at Costco!

• Use a jumbo muffin tin to get the right size.
• Sprinkle extra chocolate chips on top just before baking.
• Bake at a higher temperature (375°F) to help create that nice domed top.

And don’t forget to fill each muffin cup ¾ full too. It’s another crucial step to getting the bakery look and feel!

Storage and Reheating

Chocolate muffin batter will keep in the refrigerator for up to 24 hours if you want to whip it up the night before you plan on baking!

Baked muffins will keep in an airtight container at room temp for up to 3 days. 

Alternatively, store them in the fridge for up to 1 week or in the freezer for 3 months. I suggest wrapping each muffin separately in plastic wrap first if you do want to freeze them!

Thaw frozen muffins at room temperature or warm in the microwave for 20-30 seconds until warmed through.

Costco Double Chocolate Muffin FAQ

Enjoy!

With love, from our simple kitchen to yours.

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Originally published May 2025

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