It’s my brother-in-law’s birthday and this year I wanted to recreate the epic 5-layer brownie Oreo cake I made him in 2016.

His lucky number is 5, and he jokingly said he’d like a five-layer cake.

Little did he know, his comment would result in this ginormous cake!

It has alternating layers of tender Oreo cake and brownies and is frosted with homemade Oreo buttercream.

While this cake does have a few different components, it’s totally worth the effort!! I recommend making this cake in stages so that you can enjoy the process.

How to Make This Brownie Oreo Cake

To make sure this cake turns out as amazing as possible, let’s walk through each step together!

I’ve also included a video tutorial of the process below.

Step 1: Make the Oreo Cake Layers

Make the Oreo cake layers first. Once the batter is made, pour it evenly between the prepared, 8-inch cake pans.

I like to use a scale to make sure each pan has the same amount of batter and will bake up to be the same height.

Bake for 34-36 minutes or until a toothpick comes out with a few moist crumbs.

Let the pans cool for 10 minutes, then run an offset spatula around the perimeter of the pan to separate the cake from the pan.

Once the layers are fully cooled, carefully flip the pans and remove the layers from the pans. Use a serrated knife to level the tops of the cooled cake layers.

If you make these in advance, wrap and freeze them at this point. When you’re ready to use them, let them thaw for about 20 minutes before making your cake.

The cake layers should still be slightly cold to the touch, which will make it easier to assemble your cake.

Step 2: Make the Brownie Layers

Next, make the brownies! It’s a big batch, but we need a lot of brownies to fill the cake and decorate it.

Line and grease 2 round, 8-inch cake pans and 1 square, 8-inch cake pan.

Divide the batter evenly between the prepared pans.

Bake in a preheated oven for 43-53 minutes. The circular pans should take about 5 minutes longer to bake than the square pan.

Remove from the oven and let the pans cool on wire rack, then set aside.

Step 3: Make the Oreo Buttercream

While the cake layers and brownies bake and cool, make the Oreo buttercream frosting.

Mix the frosting on the lowest speed with a paddle attachment once it’s made to push out any excess air, then add in the crushed Oreos.

I also like to stir the frosting by hand with a rubber spatula once it’s fully made. This makes the frosting nice and smooth and easier to smooth onto your cake.

If the frosting seems too thick, add in additional cream (1 Tbsp at a time). If the frosting is too thin, add in more powdered sugar (quarter of a cup at a time). Cover with plastic wrap and set aside.

This frosting can also be made in advance and kept in the fridge for up to a month.

Step 4: Assembling This Oreo Brownie Cake

Stack and frost the alternating Oreo and brownie layers on a greaseproof cake board using a dab of frosting to help stick the first cake layer to the board.

Add an even layer of Oreo buttercream between each cake layer and brownie layer.

Spread a thin coat of frosting around the the cake to fully cover the cake layers.

Smooth using a bench scraper, then chill the cake in the fridge (30 minutes) or freezer (10 minutes) until the frosting is firm to the touch.

Step 5: Spread on a Thick, Second Layer of Frosting & Decorate

Add a second, thicker layer of Oreo frosting to the cake and smooth using a bench scraper.

If you want to add a drip around the cake, use my chocolate ganache drip recipe.

Cut up the remaining square pan of brownies into small, 1-inch squares.

Use them to decorate the top of the cake with buttercream swirls and Oreos, then enjoy! Use a sharp, warm knife to cut clean slices.

Brownie Oreo Cake Recipe Variations

This recipe can also be used to make a sheet cake! One batch will make 2, 9-inch x 13-inch cake layers that are about 1 inch tall.

Use the brownie batter to bake one 9-inch x 13-inch sheet pan of brownies and place it in between the cake layers.

Tips for Making the Best Brownie Oreo Layer Cake

• Ingredients at room temperature mix together better! Set out any cold ingredients ahead of time.
• Properly measure your flour (spoon into the cup measure, then level). Or better yet, use a kitchen scale to measure your dry ingredients.
• Mix the cake batter just until the ingredients are incorporated. This will ensure your cake layers are tender and fluffy.
• Use a scale to weigh your cake pans as you fill them. It will make your cake layers bake to the same height and bake more evenly.
• Bang your cake pans on the counter before putting it in the oven. This brings any big air bubbles that are trapped in the batter to the surface.
• Level your room temperature or thawed cake layers with a serrated knife to make them easier to stack.
• Chill your cake layers in the freezer for about 20 minutes before assembling the cake. It makes it so much easier to stack and frost them!

Making This Brownie Oreo Cake in Advance & Storage Tips

Make your cake layers and brownies in advance and freeze them. It breaks the process up and makes it more approachable.

Make your frosting ahead of time too or save any leftover frosting! It can be stored in an airtight container in the fridge for up to a month, or in the freezer for up to 3 months. Be sure to give it a good stir once it thaws to get the consistency nice and smooth again.

A frosted cake can last in the fridge for up to a week, or in the freezer for up to a month. The buttercream locks in all the moisture, keeping the cake fresh and delicious!

If you cut into the cake and have leftovers, use any remaining frosting to cover the cut section to keep it moist and store in the fridge for up to a week.

Let Me Know What You Think

If you try this brownie Oreo cake recipe, I’d love to hear what you think! Please leave a rating below and comment below.

Don’t forget to tag me @chelsweets and use #chelsweets on social media so I can see your amazing creations!

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For a walk down memory lane, below are some picture from when I first made this cake in 2016.