Crumble the sponge cake into fine crumbs in a mixing bowl.
Add the icing sugar to the cake crumbs and mix until well combined.
Roll the mixture into small, bite-sized balls and place them on a baking sheet lined with parchment paper.
In a heatproof bowl, break the dark chocolate and milk chocolate into small pieces.
Melt the chocolate by placing it over a pan of simmering water (double boiler). Stir until the chocolate is smooth and fully melted.
Using a fork or a skewer, dip each cake ball into the melted chocolate, ensuring it’s completely coated. Allow any excess chocolate to drip back into the bowl.
Place the chocolate-covered cake balls back on the parchment paper.
If desired, sprinkle the cake balls with your choice of decorations, such as sprinkles or crushed nuts, while the chocolate is still wet.
Allow the chocolate-covered cake balls to cool and set for a few minutes.
Place the cake balls in the refrigerator for about an hour to firm up.
Once the chocolate is fully set, your chocolate-covered cake balls are ready to enjoy.
