Prepare the Crumbs: Place your cake pieces into a food processor and pulse until they resemble fine sand. Alternatively, crush them by hand in a large bowl using a fork or your fingers. The texture should be uniform without large chunks.
Mix the Base: Transfer the crumbs to a mixing bowl. Add the softened frosting and vanilla extract (if using). Mix with a spatula until fully combined. The mixture will look dry at first but should come together when pressed.
Chill the Mixture: Cover the bowl tightly with plastic wrap and refrigerate for at least 30 minutes. This step is crucial; cold crumbs are easier to roll into smooth, tight balls that won't crack during coating.
Form Truffles: Line a baking sheet with parchment paper. Scoop about 1 tablespoon of mixture per truffle. Roll between your palms firmly but gently until you have smooth spheres. Place them on the lined sheet. Return them to the fridge for another 15 minutes while you melt the chocolate.
Melt Chocolate: In a microwave-safe bowl, combine chocolate chips and coconut oil. Microwave in 30-second intervals, stirring well between each interval, until completely smooth and glossy. Do not overheat, or the chocolate may seize.
Coat Truffles: Remove truffles from the fridge. Using a fork, dip one truffle at a time into the melted chocolate, turning it to coat evenly. Lift the fork out and tap gently against the side of the bowl to remove excess chocolate. Let the excess drip off for a few seconds.
Set and Decorate: Gently slide the coated truffle onto the parchment-lined baking sheet. Immediately sprinkle with sprinkles before the chocolate sets. If adding "dirt" (sesame seeds/cookie crumbs), apply them while the chocolate is still wet.
Final Set: Allow the truffles to sit at room temperature for 10–15 minutes until the chocolate hardens, or place in the refrigerator for 20 minutes to speed up the process. Store in an airtight container in the fridge.
