Prepare the Cake Crumbs: Crumble your cooled vanilla sponge cake into a large bowl. You can do this with your hands or by pulsing it a few times in a food processor until you have fine crumbs. Ensure there are no large lumps remaining.

Make the Frosting Binder: In a separate bowl, using a stand mixer or an electric hand mixer, beat the softened butter and room temperature cream cheese together until smooth and creamy, about 2-3 minutes. Gradually beat in the sifted icing sugar until well combined, then mix in the vanilla extract.

Combine Cake and Frosting: Add about three-quarters of the frosting to the cake crumbs. Mix it in with a spatula or your hands until the mixture comes together and holds its shape when squeezed. It should have a consistency similar to play-doh. Add more frosting if it seems too dry, but be careful not to make it too wet.

Shape the Trees: Line a baking tray with parchment paper. Take about 2 tablespoons of the cake mixture and roll it into a ball, then gently shape it into a cone. Place the cone on the prepared baking tray. Repeat with the remaining mixture to make approximately 24 trees.

First Chill: Place the baking tray with the shaped trees into the refrigerator to chill for at least 1 hour, or in the freezer for 30 minutes. They need to be very firm before dipping. I find the freezer works best when I'm short on time.

Melt the Coating: Just before the chilling time is up, melt the green candy melts in a microwave-safe bowl. Heat in 30-second intervals, stirring well between each, until smooth. If the mixture is too thick, stir in 1 tablespoon of vegetable or coconut oil to thin it out for easier dipping. A deep, narrow glass or mug is ideal for this.

Dip the Trees: Remove the chilled cake cones from the freezer. Working one at a time, dip a cone into the melted candy, using a fork to lift it out and gently tapping the fork on the side of the bowl to allow excess coating to drip off.

Decorate and Set: Place the coated truffle back on the parchment-lined tray. Immediately, before the coating sets, add your sprinkles and place a yellow star sprinkle on top. Once you've dipped a few, carefully insert a small pretzel stick into the base of each tree to create the trunk.

Final Set: Let the Christmas Tree Cake Truffles set completely at room temperature for about 30 minutes, or speed up the process by placing them in the fridge for 10-15 minutes until the coating is hard.