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image of an octopus cake made with colorful cake layers and homemade buttercream
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5 from 12 rating

Octopus Cake

This octopus cake is just fun to make as it is eat! It's made with colorful swirled cake layers and frosted with buttercream frosting.
Prep Time15 minutes
Cook Time34 minutes
Additional Time2 hours
Total Time2 hours 49 minutes
Course: Cakes
Cuisine: American
Servings: 24
Calories: 687kcal
Author: Chelsey White

Ingredients

Swirled Cake Layers

  • 3 cups all-purpose flour 390 grams
  • 3 cups granulated sugar 600 grams
  • 2 1/2 tsp baking powder 10 grams
  • 1 tsp fine salt 6 grams
  • 1 cup unsalted butter, room temperature 226 grams - 2 sticks
  • 1 cup carton egg whites, room temperature or about 7 egg whites (235 grams)
  • 1 1/2 cups full-fat sour cream, room temperature 380 grams
  • 2 Tbsp vegetable or canola oil 28 grams
  • 2 tsp vanilla extract or vanilla bean paste 8 grams
  • blue and purple gel food coloring - optional

Vanilla Buttercream Frosting

  • 3 cups unsalted butter, room temperature 678 grams
  • 1 Tbsp vanilla extract or vanilla bean paste 12 grams
  • 1 tsp fine salt 6 grams
  • 11 cups powdered sugar 1375 grams
  • 1/3 cup heavy whipping cream, room temperature or whipping cream (75 grams)
  • blue and purple gel food coloring - optional

Rice Krispie Treats - Octopus Legs

  • 5 cups mini marshmallows 250 grams
  • 7 cups puffed rice cereal 175 grams

Octopus Cake Decoration

Instructions

Step 1: Make the Colorful Cake Layers

  • Preheat oven to 350°F / 175 C. Grease and line two 7-inch cake pans, two 6-inch cake pans and set aside.
  • Mix together 3 cups all purpose flour, 3 cups sugar, 2 1/2 tsp baking powder and 1 tsp salt in a stand mixer with a paddle attachment or hand mixer on a low speed until combined.
  • Mix in 1 cup of unsalted butter slowly into the dry ingredients on a low speed. Continue to mix until no large chunks of butter remain and the mixture looks crumbly.
  • Pour in 1 cup of egg whites and mix on low until just combined.
  • Mix in 1 1/2 cups sour cream on a low speed, 2 Tbsp of vegetable oil and 2 tsp of vanilla extract. Mix at a low speed until incorporated.
  • Scrape down the sides of the bowl with a rubber spatula then beat on a low speed for about 30 seconds to make sure everything is properly mixed together.
  • Divide the batter evenly between three bowls and color them purple, light blue and and dark blue using gel food coloring.
  • Add spoonfuls the colorful batter into the prepared pans, then use a small offset spatula or a butter knife to swirl the batter together.
  • Bake the cake layers 34-36 minutes, or until a toothpick comes out with a few moist crumbs. Rotate the pans halfway through baking to help them bake more evenly.
  • Once the cake layers are out of the oven, run a small offset spatula around the edges of the pans to help separate the cake layer from the pan.
  • Allow the layers to cool in the pan for about 15 minutes, then flip them onto a wire rack to finish cooling.
  • Once the cake layers have finished cooling use a serrated knife to level the tops and set the cake layers aside.
  • Use a serrated knife to trim the edge of one of the 6-inch cake layers to give the octopus head a rounder shape.
  • If you're making these cake layers in advance, wrap and freeze them like this. When you're ready to assemble the cake, unwrap the frozen layers and allow them to thaw for about 30 minutes before you plan to frost the cake.

Step 2: Make the Vanilla Buttercream Frosting

  • While the cake layers bake and cool, make the buttercream frosting.
  • Beat 3 cups of butter on a medium speed for 30 seconds with a paddle attachment or hand mixer until smooth.
  • Add in 1 Tbsp of vanilla extract and 1 tsp of salt and mix on a low speed.
  • Slowly mix in 11 cups of powdered sugar on a low speed. Add 1/3 cup of heavy cream half way through to make it easier to mix.
  • Once fully mixed and has reached the desired consistency, beat on low until for a couple extra minutes to make the frosting super smooth and to push any extra air out of the frosting.
  • If the frosting is too thick, add in additional cream (1 Tablespoon at a time). If the frosting is too thin, add in more powdered sugar (quarter of a cup at a time).
  • Wait to color the frosting until the cake is crumb coated. Cover the buttercream with plastic wrap to prevent crusting, then set aside.

Step 3: Assemble this Octopus Cake

  • Stack and frost cake layers on a 10-inch greaseproof cake board using a dab of frosting to help stick the first cake layer to the board.
  • Add an even layer of buttercream between each cake layer with a large offset spatula, and stack them in the following order: 6-inch, 7-inch, 7-inch, trimmed 6-inch.
  • Spread a thin coat of frosting around the the cake to fully cover the cake layers. Smooth using a bench scraper and/or acetate sheet, then chill the cake in the fridge (20 minutes) or freezer (10 minutes) until the frosting is firm to the touch.

Step 4: Make the Octopus Legs with Rice Krispie Treats

  • While the crumb coat chills, make the cake-decorating friendly rice krispies to create our octopus arms.
  • Place 5 cups of mini marshmallows in a heatproof bowl and heat in the microwave for 30 seconds at full power.
  • Stir then heat in 15 second intervals until the marshmallows are melted (mine usually take a total of 1 minute to melt fully).
  • Pour in 7 cups of rice krispies or puffed rice cereal and stir until the cereal is fully coated in melted marshmallows.
  • Grease your hands with cooking spray then shape 8 legs by compacting the rice krispies into elongated triangles. Place the legs against the cake as you make them to make sure they're proportionate, shaped properly, and will all fit around the cake.

Step 5: Decorate this Octopus Cake

  • Press the rice krispie treat legs into place around the base of the chilled cake. They should still be slightly warm and should stick in place with a bit of pressure. If they're not sticking, use a little extra buttercream to keep them in place.
  • Scoop 1/2 cup of frosting into a bowl and color it a light shade of purple with gel food coloring. Place this frosting a small piping and set aside. Color the remaining buttercream blue with gel food coloring.
  • Add a second, thicker layer of blue buttercream around the cake and top of the rice krispies. Smooth using a small offset spatula and an acetate sheet.
  • Pipe the light purple buttercream underneath each rice krispie tentacle, and smooth using a small offset spatula and an acetate sheet.
  • Chill the cake again in the fridge (20 minutes) or freezer (10 minutes) until the second coat of frosting firms up.
  • If desired, color the leftover purple frosting a deeper shade of purple and place in a piping bag fit with a small round piping tip (or just snip the end of the bag to create a small hole). Pipe small circles underneath each of arms over the light purple frosting.
  • Place the fondant facial features on the chilled cake with a small dab of buttercream.
  • Let the cake sit out at room temperature for 1-2 hours before serving to make it easier to cut.

Video

Notes

Tips for Making The Best Octopus Cake

  • Try to be patient and give yourself lots of time! Sculpted cakes like this can be challenging. Take your time smoothing the frosting and adding on the details to this cake.
  • Be sure to properly measure your flour (spoon into the cup measure then level) or use a kitchen scale to measure your dry ingredients.
  • Use gel food coloring to create vibrant colors of frosting without throwing off the consistency of the frosting or giving it a bitter taste.
  • Ingredients at room temp mix together better, so be sure you set out any cold ingredients ahead of time.
  • Mix your cake batter just until the ingredients are incorporated. This will ensure your cake layers are tender and fluffy.
  • Chill your cake layers in the freezer for about 20 minutes before assembling the cake. This makes it easier to stack and frost.
  • Make this octopus cake vegan or dairy free if needed! Use your favorite type of dairy free milk to replace the buttermilk and heavy cream, and use vegan butter sticks in place of the butter. For the eggs I recommend using an egg replacer like this.
  • Use an acetate sheet to help you get your final coat of frosting super smooth.

Making this Cake in Advance

Make your cake layers in advance and freeze them. It breaks the process up and make 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.

Nutrition

Serving: 1 | Calories: 687kcal | Carbohydrates: 92g | Protein: 4g | Fat: 35g | Saturated Fat: 20g | Polyunsaturated Fat: 13g | Cholesterol: 86mg | Sodium: 297mg | Sugar: 78g