Crumble the *chocolate sponge cake* into a large mixing bowl. The texture should be fine crumbs to ensure an even mix with the cream.

In another bowl, beat the *butter* until smooth. Add the *dulce de leche* slowly, continuing to beat until the mixture becomes creamy and well-blended.

Add the prepared cream mixture to the bowl of cake crumbs. Mix thoroughly using a spoon or your hands until it reaches a dough-like consistency.

Form the mixture into oval-shaped 'potatoes,' compacting them firmly so they hold their shape well.

Melt the *milk chocolate* and *white chocolate* together in a heat-safe bowl over simmering water or in a microwave using short bursts, stirring frequently. Mix just enough to blend the colors but maintain a marbled pattern.

Dip each 'potato' evenly in the chocolate mixture and place on a rack to allow any excess to drip off. While the coating is still wet, dust lightly with *cocoa powder* to give an earthy, 'potato-like' appearance.

If desired, use melted *white chocolate* to create small sprouts on each potato for a fun effect.

Let the coated 'potatoes' set in the refrigerator for at least 30 minutes before serving. Enjoy your easy-to-make, delightful dessert with its surprise *jelly heart* inside!