# What You'll Need:
→ Vanilla cake
01 - 3 cups all-purpose flour
02 - 2 1/2 teaspoons baking powder
03 - 1/2 teaspoon fine salt
04 - 1 cup unsalted butter (2 sticks), room temperature
05 - 2 cups granulated sugar
06 - 4 large eggs, room temperature
07 - 1 tablespoon vanilla extract
08 - 1 1/4 cups whole milk
→ Buttercream
09 - 2 cups unsalted butter (4 sticks), room temperature
10 - 6 cups powdered sugar, sifted
11 - 2 teaspoons vanilla extract
12 - 3 to 4 tablespoons heavy cream or milk, as needed
13 - Teal gel food coloring, quantity as needed
→ Geode decoration
14 - 2 cups rock sugar crystals (clear or white)
15 - Teal gel food coloring, a few drops
16 - Edible gold leaf or gold luster dust plus a small amount of clear alcohol (e.g., vodka) for painting
→ Assembly
17 - Simple syrup (optional), as needed for moistening layers
# How To Make It:
01 - Preheat the oven to 350°F. Grease and line three 8-inch round cake pans. Whisk together the flour, baking powder and salt in a bowl. In a separate large bowl, cream the butter and sugar until pale and fluffy. Add the eggs one at a time, incorporating each fully, then stir in the vanilla. Alternately add the dry mixture and the milk to the butter mixture, beginning and ending with the dry ingredients, mixing just until combined. Divide the batter evenly among the prepared pans and bake 28 to 32 minutes, or until a toothpick inserted into the centers comes out clean. Let the layers rest in the pans 10 minutes, then turn out onto cooling racks and cool completely.
02 - Using an electric mixer, beat the butter until smooth and creamy. Gradually add the sifted powdered sugar, mixing on low at first, then increase speed until well combined. Add the vanilla and 3 tablespoons of heavy cream, adjusting with the remaining tablespoon until the frosting reaches a spreadable consistency. Reserve a small portion of uncolored buttercream for the crumb coat and tint the majority teal with gel coloring to the desired shade.
03 - Place the rock sugar crystals in a bowl and add a few drops of teal gel food coloring. Gently toss the crystals until evenly colored; spread them on parchment to dry if they become slightly tacky.
04 - Level the cooled layers if necessary. Optionally brush each layer with simple syrup to add moisture. Place one layer on a cake board, spread a thin even layer of teal buttercream, then repeat with the remaining layers. Apply a thin crumb coat using the reserved uncolored buttercream, smooth the surface, and chill the cake 20 minutes to set the crumb coat.
05 - Frost the entire cake smoothly with the teal buttercream. Using a sharp serrated knife, carefully carve a wedge-shaped cavity into the side of the cake to expose the interior where the geode will sit. Apply a thin layer of buttercream inside the carved cavity to act as an adhesive for the crystals.
06 - Press the teal-colored sugar crystals into the buttercream-lined cavity, using lighter-toned crystals toward the center and darker or more saturated crystals at the edges to create depth. Apply edible gold leaf to the edges of the cavity or paint the border with gold luster dust mixed with a little clear alcohol for a metallic finish. Add any additional gold accents and a graduation topper if desired.
