Giant Costco Copycat Gluten Free Chocolate Zucchini Muffins

This recipe is AGE OLD. I remember my mom making giant chocolate zucchini sheet cakes and covering them with her homemade fudge sauce when I was maybe 5 or 6 years old for any and every potluck or family event. It was hands down my favorite chocolate cake, maybe one of my favorite desserts (which, let me tell you, is a really difficult question to answer as a 5 or 6 year old – there are so many favorites!). I went on to make chocolate zucchini cakes for friends for their birthdays, especially for Christina who is the number one chocolate zucchini cake fan EVER. I even brought a ziplock baggie filled with the dry ingredients for chocolate zucchini cake in my carryon luggage to Vienna when I visited her years ago and had a brief but thankfully uneventful encounter with a confused TSA agent who didn’t understand why I’d want to pack a bag of brown dust. WORTH IT. So, here I give you the ultimate GIANT gluten free chocolate zucchini muffins – a personal-sized treat reminiscent of that sheet cake mom made for us as kids. Complete with ganache because why the heck not.

Back to the giant muffins! So far we’ve made these giant poppyseed muffins, giant blueberry muffins, giant chocolate chip muffins, giant double chocolate muffins, giant banana nut muffins, giant strawberry rhubarb muffins, giant apple streusel muffins, these giant lemon raspberry muffins, giant cherry chocolate chip muffins, these giant coffee walnut muffins, these giant pistachio apricot muffins, these giant orange marmalade muffins, these giant zucchini muffins, these giant mango muffins, and these giant peach crumble muffins!

Tips for Delectable Giant Chocolate Zucchini Muffins:

A few tips for getting these to turn out just like you remember those Costco muffins:

• Use the right-size of pan! Apparently, Costco keeps their giant muffin pans as a trade secret because we can’t find them ANYWHERE on the internet and you can find EVERYTHING on the internet. Bravo, Costco, for a secret well-kept. However, we’ve found a way to crack the code and gone ahead and just used these brilliant 4-inch cake pans because, after careful inspection, we’ve discovered that Costco muffins are exactly 4-inches in diameter! HA! Take that, Costco-bakery-lords. I never thought I’d be regularly using 4-inch cake pans but here we are. I’ll just need to make a bunch of tiny cake recipes next!
• Pack in that zucchini! Don’t skimp on the amount of grated zucchini you use – be sure to press it down in the measuring cup to get all those veggies!
• Let your batter REST, per the recipe, for at least 30 minutes. For two reasons: 1) the batter thickens as it rests; and 2) something somewhere said that baking powder needs a bit more time to “activate.” Don’t quote me on this, who knows if it’s actually true.
• Don’t over-mix your batter! Muffins need a lot of lift, especially these giant ones, and if you over-mix your batter, you’ll end up with flat or sunken muffins which is no fun.
• Use a good 1-1 gluten free flour mix! We use the Bob’s Red Mill one (the baking mix), though we’ve heard good things about Cup-4-Cup. We’ve only tested this recipe with this one so if you want them to turn out exactly like ours, we recommend snagging a bag of that specific 1-1 gluten free flour.
• Use good-quality cocoa powder – preferrably dutch processed (link to my favorite) (or “dutched”) cocoa powder! This gives the cocoa a smoother, (I think richer) flavor and a deeper color, which makes for a stunning final product.
• Do NOT open the oven door during baking time. Tape it shut if you have to! You can certainly turn on the oven light and peek and the gloriousness that is a set of rising muffins nearly-ready to be devoured, but do not open that door! Opening the door will immediately lower the oven temp and prohibit your muffins from rising correctly. If you’re in the last few minutes of baking and need to test to see if they’re done, open the oven just a tiny bit and reach in and just tap the top of one – if it springs back it’s done, if it presses in like a foam mattress topper, it’s not and needs a couple more minutes!
• These will keep in an airtight container for a week or so – and they freeze REALLY well! So if you want to make a batch and save a bunch, put them in a sturdy plastic container or a freezer plastic bag and pop them in there. Then microwave for about 30-45 seconds (from frozen) before eating! I even like popping mine in the microwave for 10-15 seconds from room temp to get them all warm and floofy again before eating.
• Ganache: ganache sounds and looks hella fancy but it’s actually one of the easiest things you’ll EVER make. Literally. Ever. Just pop cream in the microwave, pour it over chocolate chips (fancy chocolate if you want to but you don’t need to), stir, and voila! It will look like a total mess when you first start stirring – never fear, just keep stirring and magic will happen. You can also use any leftover ganache to fill cupcakes, pour over ice cream, or just eat with a spoon (we won’t tell anyone).

Print Recipe

5 from 1 vote

Giant Gluten Free Chocolate Zucchini Muffins

These unbelievably rich chocolate zucchini muffins are fluffy, moist, and covered in silky ganache!

Prep Time20 minutes mins

Cook Time45 minutes mins

Resting time30 minutes mins

Course: Breakfast, Dessert, Snack

Cuisine: American

Diet: Gluten Free

Keyword: breakfast, chocolate, costco muffins, easy, ganache, giant, gluten free, healthy breakfast, muffins, simple, zucchini

Servings: 6 giant muffins

Calories: 550kcal

Author: Amelia Farber

Equipment

• Six 4-inch round cake pans (link below to the ones we use)
• Cookie sheet

Ingredients

For the muffins:

• 4 large eggs
• 2 Cups white sugar
• 1 1/2 Cups canola oil
• 2 tsp vanilla extract
• 2 Cups gluten free 1-1 flour mix with xanthan gum added (if it doesn't have xanthan gum, add 1 teaspoon xanthan gum) link below to the one we use
• 3/4 Cup dutched Cocoa powder
• 1/2 tsp ground cinnamon
• 1 1/4 tsp baking soda
• 2 tsp baking powder
• 3/4 tsp salt
• 3 Cups packed grated zucchini do not squeeze out the liquid

For the ganache:

• 1/2 Cup heavy cream
• 1 Cup chocolate chips

Instructions

• First, make your muffin batter! It will need to rest for 30 minutes before baking. In a large bowl, whisk together the eggs, sugar, oil, and vanilla. Then stir in the gluten free 1-1 flour mix, dutched cocoa powder, baking powder, baking soda, cinnamon, and salt. Finally, fold in the three packed cups of grated zucchini and the 1 1/2 cups of chopped walnuts until just combined. Do not over-mix or your muffins won't rise. Let the batter sit at room temp for 30 minutes.
• Once rested, preheat the oven to 350° Fahrenheit and place your six 4-inch cake pans on a cookie sheet. Spray each pan with cooking spray, then spoon batter into each one evenly (they should be about 2/3-3/4 full). Bake for 40-45 minutes until the tops spring back with touched (do NOT open the oven while baking or the muffins will deflate. To check if done, open the oven only once very little and tap muffin with your finger). Let cool nearly-completely before turning out and covering with ganache.
• While the muffins are cooling, make the ganache. Place the chocolate chips in a medium bowl, then heat the 1/2 cup of cream in the microwave (about a minute) or on the stovetop until simmering, then pour over the chocolate chips to cover them and let sit one minute. Then stir with a cereal spoon until fully melted/combined (this will take a while – it will look weird at first!). Once smooth, you can either pour it through a sieve to remove any tiny lumps, or just pour straight on your muffins (once you've taken them out of their pans), and serve!
• You can let the ganache-covered muffins sit at room temp for 30-45 minutes for the ganache to set, then put into containers and keep in the fridge or freezer for up to a week. Best-served slightly warm, so pop them in the microwave for 10-20 seconds from room temp!

Tag @sisterssansgluten on Instagram if you snap a photo of your muffins!

Food photography and styling by Amelia Farber