Once cake has cooled, break it into pieces and place in a bowl. Add frosting. Using your hands mix everything together until it's cohesive. If you prefer, you can do this in the bowl of a stand mixer and use the paddle attachment to mix to combine.
Divide white chocolate or candy melts into 3 separate bowls, putting ¾ cup in each bowl. Place one bowl in the microwave and melt (I recommend using 50% heat for 1 minute and then stirring before placing back in the microwave and using 50% heat for 30 seconds. Take out and stir. Continue until chocolate is melted). If you prefer to use a double boiler, you can. Add 3-4 drops of yellow food coloring to melted chocolate and stir to combine.
Spoon a little of the yellow chocolate into the bottom your cakesicle mold and using a small off-set spatula or a pastry brush, evenly distribute chocolate along the bottom of the mold and up the sides. Place in the fridge for 5 minutes to harden. Upon removal, check sides of molds and if the chocolate looks thin, brush a little more on and let harden again.
Take one of the popsicle sticks and insert it into the mold and then remove it. This is simply to ensure that the chocolate doesn't harden over the opening as you'll need to insert the stick later.
While cakesicles are in fridge repeat melting process with second bowl. Add 3-4 drops of orange food coloring. Evenly distribute the orange chocolate to the middle of the mold, along the bottom and up the sides. Again, pop in the fridge for 5 minutes. Check sides and add more chocolate to thicken if necessary.
Repeat melting process with third bowl and keep mixture white. Finish by coating the top of the mold with the white, again, being sure to go up the sides. Let harden in the fridge for 5 minutes. Check sides and add more chocolate to thicken if necessary.
Put a little more than 1 Tbsp of cake mixture over the hardened chocolate in each mold and press down. Make sure it's nice and smooth with no crumbs and that it's just below the lip of the mold. Insert a popsicle stick into each mold and press down on the cake again.
Coat the cake with more melted white chocolate (color of your choice or you can repeat the yellow, orange, and white pattern) to cover the backs of the cakesicles. Place in the fridge for 5 minutes to harden.
Gently remove cakesicles from their molds. You'll have to wiggle them a little and take care when pushing the popsicle stick out.
If you want to decorate the cakesicles (I didn't with the candy corn ones, but did with the other Halloween ones), simply brush a little more melted chocolate on to adhere sprinkles, candy eyes, etc.