Geode Cake

Geode Cake

The Spruce/ Kristina Vanni

Prep: 45 mins
Cook: 30 mins
Cool Cakes: 2 hrs
Total: 3 hrs 15 mins
Serving: 1 slice
Yields: 12 slices
Nutritional Guidelines (per serving)
7749 Calories
398g Fat
986g Carbs
75g Protein
See Full Nutritional Guidelines Hide Full Nutritional Guidelines
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Nutrition Facts
Servings: 1
Amount per serving
Calories 7749
% Daily Value*
Total Fat 398g 510%
Saturated Fat 240g 1,202%
Cholesterol 1749mg 583%
Sodium 3064mg 133%
Total Carbohydrate 986g 358%
Dietary Fiber 7g 25%
Total Sugars 638g
Protein 75g
Vitamin C 4mg 18%
Calcium 1568mg 121%
Iron 36mg 199%
Potassium 1450mg 31%
*The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.
(Nutrition information is calculated using an ingredient database and should be considered an estimate.)

Geode cakes are stunningly decorated layer cakes meant to mimic the famous natural formation of rock and precious and semiprecious stones. Pieces of the finished and frosted cake are cut out, and then the cavity is filled with edible crystals made out of rock candy. Although it might seem like a lot of work, it actually isn't much more than making a layered and frosted cake, especially if you're buying the rock candy and not making it (you could, using isomalt). Use loose rock candy or the classic rock candy on a stick—just remove it from the stick before arranging it on the cake.

To make a realistic geode cake, decide on your favorite color palette for the geode. Start by selecting the main color of the stones—any hue will be beautiful. Purchase either a lighter shade of that same color or white rock candy to help create the ombré effect similar to that of real rock formations. Finally, purchase edible gold dust, gold shimmer sprinkles, or flakes to paint around the edges of the geode formation.

The amount of candy needed depends on how much you'd like to use on the cake and on how many cutouts you want it to have. The best course of action is to place enough candy to cover all the surfaces without crowding them. Rock candy crystals come in bags of one pound or more, so you'll get enough for this three-layer cake when you buy a one-pound bag each of colored and white candy. For easy decoration, we suggest you have at hand an offset spatula and food tweezers to easily frost the cake and place the rock candy in its place.

Ingredients

For the Cake:

  • 1 cup unsalted butter, softened

  • 2 cups sugar

  • 4 large eggs

  • 3 cups cake flour, sifted

  • 1 tablespoon baking powder

  • 1/2 teaspoon salt

  • 1 cup milk

  • 1 1/2 teaspoons vanilla extract

For the Buttercream Frosting:

  • 2 (1-pound) boxes powdered sugar

  • 1 cup unsalted butter, softened

  • 6 to 8 tablespoons milk, divided

  • 2 teaspoons vanilla extract

For the Decoration:

  • Colored rock candy

  • White rock candy

  • Edible gold dust

Steps to Make It

Note: While there are multiple steps to this recipe, this cake is broken down into workable categories to help you better plan for preparation, baking, and decoration.

Make the Cakes

  1. Gather the ingredients.

    Ingredients for making a geode cake

    The Spruce / Kristina Vanni

  2. Preheat the oven to 350 F. Grease and flour 3 (8-inch-round) baking pans. Alternatively, if you only have 1 or 2 (8-inch-round) baking pans, each layer can be baked one at a time. In a large bowl, cream together the butter and sugar until light and fluffy, either by hand or with the help of a standing mixer set with the paddle attachment.

    Butter and sugar in a mixing bowl

    The Spruce / Kristina Vanni

  3. Add the eggs one at a time to the creamed mixture, beating well after each addition.

    Adding eggs to the creamed butter and sugar

    The Spruce / Kristina Vanni

  4. In another large bowl, mix together the cake flour, baking powder, and salt.

    Cake flour, baking powder, and salt in a bowl

    The Spruce / Kristina Vanni

  5. Add the flour mixture to the butter mixture, alternating it with the milk and vanilla extract. Mix well after each addition until you have a smooth batter. Do not overbeat.

    Getting ready to add flour mixture to butter mixture

    The Spruce/ Kristina Vanni

  6. Evenly divide the batter into the 3 prepared pans. Bake for 20 to 25 minutes or until a tester inserted into the cake comes out clean.

    Geode cake batter in three 8-inch-round pans

    The Spruce / Kristina Vanni

  7. Cool in the pans for 10 minutes. Remove cake layers from the pans and cool completely on wire racks for 1 to 2 hours. The cakes need to be completely cold before frosting them.

    Three round cakes cooling on a wire rack

    The Spruce / Kristina Vanni

Make the Buttercream and Frost the Cake

  1. To prepare the buttercream frosting, combine the powdered sugar, butter, 6 tablespoons of the milk, and the vanilla extract in the large bowl of a standing mixer. Using the whip attachment, beat at medium speed for 1 to 2 minutes, until creamy. If necessary, add more of the remaining milk, half a tablespoon at a time, until the frosting achieves the desired consistency.

    Powdered sugar and butter for making the frosting

    The Spruce / Kristina Vanni

  2. Place the first cake layer on a serving platter or cake stand. Top with some of the buttercream frosting. Place another layer on top and repeat the above process. Place the third layer and cover in frosting.

    Topping a cake with buttercream frosting

    The Spruce / Kristina Vanni

  3. Using the remaining frosting, evenly coat the top and sides of the 3-layer cake. Reserve a small amount of frosting to adhere the rock candy pieces when decorating.

    Geode cake covered in buttercream frosting

    The Spruce / Kristina Vanni

Carve Out and Decorate the Cake

  1. Using a small, serrated knife cut out the shape of your geode.

    A section of cake is removed for a crevasse

    The Spruce / Kristina Vanni

  2. Frost the crevasse with the remaining frosting and press the colored rock candy into the deepest part of the crevasse and most of the way up the sides.

    Cake crevasse frosted and studded with purple rock candy

    The Spruce / Kristina Vanni

  3. Use the white rock candy to surround the colored rock candy.

    Purple rock candy is edged with white rock candy

    The Spruce / Kristina Vanni

  4. Use the edible gold dust to paint the edges around the white rock candy. 

    Cake crevasse edged with edible gold dust

    The Spruce / Kristina Vanni

  5. Enjoy.

How to Store and Cut a Geode Cake

Once completed, a geode cake can be refrigerated for up to four days until ready to serve, just let the cake rest at room temperature for a whole hour before slicing. It is best to cut the geode cake from the undecorated side first, and once slices have been plated for your guests, place a few loose pieces of rock candy on the side for additional decoration.