This Instagram sensation started as a simple post. In 2016, Denver-based cake maker and Food Network Challenge winner Rachael Teufel was asked to create a cake inspired by an amethyst. She came up with a rock candy geode and shared a photo, and everyone went nuts. Now, with more than 48,000 posts, #geodecake is officially a thing: Beyoncé celebrated her birthday with a black-and-gold one. See how Rachael creates this gem.
1 cake turntable, 2 cardboard rounds (one 6 inch and one 8 inch), 1 offset spatula, 1 bench scraper, 1 small paintbrush and 3 12-inch wooden skewers
Trim the cakes to make them level. Working on a turntable, stack the 6-inch cakes on a cardboard round, spreading the buttercream between them with an offset spatula. Stack the 8-inch cakes the same way on an 8-inch round.
Cover each layer cake with a thin layer of buttercream (this is the crumb coat), smoothing it with a bench scraper. Refrigerate until firm, 1 hour. Cover with more buttercream; chill overnight. (Reserve 1/2 cup buttercream for step 4.)
Add the geode to the 6-inch layer cake: Using a paring knife, carve out an irregular piece from the side of the cake. Be careful not to cut deeper than one-third of the diameter of the cake in order to maintain the cake’s structure.
Frost the inside of the cutout, then gently add the rock candy. (Don’t press too hard or the frosting will ooze out.) Using a spoon, sprinkle sanding sugar around the edges of the cutout to fill in any gaps.
Dilute a few drops of food coloring with a splash of vodka or lemon extract. (Test your color on some spare rock candy.) Using a paintbrush, paint the center of the geode in an irregular shape; do not oversaturate.
Add a few more drops of vodka or extract to dilute the remaining food coloring; apply the lighter color around the dark center of the geode. Continue diluting the food coloring; paint outward until all the rock candy is covered.
Mix a few pinches of silver luster dust with a few drops of vodka or lemon extract. With a clean brush, paint the edges of the geode silver, then apply the gold leaf around the silver paint in spots.
Decorate the 8-inch cake, placing the geode on a different part of the cake. Insert skewers into the 8-inch cake, cutting them level to the top, then carefully add the 6-inch cake on top so the cardboard round rests flat on the skewers.