Crumble up the cake or scraps into fine crumbs in a large bowl. Add in the buttercream and mix until completely combined and the mixture can hold a shape if formed into a ball. If the cake is still crumbly, add more buttercream. With an ice cream scoop, scoop the cake mash and flatten out the top of the scoop. Press your thumb in the center to make a hole and fill the hole with jam.
Place a small amount of the cake mash on top of the jam to prevent spillage and seal up the ball. Remove the cake ball from the scoop and round it in your hands until smooth. Place on a baking sheet and freeze for 3 to 5 minutes or refrigerate for 1 hour.
Melt the chocolate coating over a double boiler or in the microwave for 30 seconds at a time, stirring in between. Add oil if too thick.
Once the cake balls are chilled and the chocolate coating is melted, drop your cake balls into the chocolate and fish them out with a fork. Place on a clean baking sheet lined with parchment paper. Set the cake balls aside to set up.
Meanwhile, roll out your modeling chocolate to create eyelids, iris and pupils and arrange on the cake balls. Cake balls can be held at room temperature.