Bake an 8-inch cake from scratch or prepare a 430–450 g boxed cake mix according to its package directions, commonly using 3 eggs, 240 ml water, and 120 ml vegetable oil. Bake for 25–30 minutes, or according to the package, then cool the cake completely before continuing.

Break the cooled cake into very fine crumbs, trimming away any very hard or browned edges from leftover cake. Add the buttercream gradually, mixing after each addition until the crumbs hold together like soft dough.

Melt about two-thirds of the candy melts, almond bark, or compound chocolate in a microwave-safe bowl using 20–30-second bursts. Stir well after every burst, and mix in 1 teaspoon of shortening or coconut oil if the coating needs to be thinner.

Spoon about 1 tablespoon of melted coating into each cakesicle cavity. Use a pastry brush or small spatula to cover the base and sides thoroughly, paying special attention to the edges and stick opening.

Insert one wooden popsicle stick into each mold while the coating is still soft. Chill the filled molds for 5–10 minutes, until the first shell is firm enough to hold its shape.

Press the cake mixture into each chilled shell, leaving a small amount of room at the top for the final chocolate layer. Pack the mixture firmly around the stick and into the corners, but stop before compressing it into a heavy, dense paste.

Cover each cake filling with more melted coating and smooth the surface with a small spatula. Chill the cakesicles for 20–30 minutes, or until the shell is completely firm.

Gently flex the silicone mold to release each cakesicle instead of pulling forcefully on the stick. Finish with melted chocolate, sprinkles, or colored candy melts, then allow the decorations to set before serving.