1. Preheat the oven to 350°F/180°C.
2. Combine the chocolate cake mix, eggs, and vegetable oil in a mixing bowl.
3. Stir until all the ingredients are well combined. The mixture will be thick, shiny, and sticky.
4. Line a baking sheet with parchment paper or lightly grease it.
5. Scoop spoonfuls of the dough onto the prepared baking sheet, spacing them a few inches apart. Use a cookie scoop or two spoons to drop them. 
6. Bake the cookies for about 10 minutes, until the edges are dry and the middle is puffed. The cookies may appear slightly undercooked in the center but will firm up as they cool.
7. Let them cool for 10-15 minutes on a wire rack until you can easily (and carefully) remove them from the baking sheet. 
8. Transfer them to a cooling rack to cool completely.
9. Repeat the process with the remaining dough until all the cookies are baked.
10. Once the cookies have cooled completely, you can store them in an airtight container for up to a week.

For the chocolate topping:

1. Heat the cream in a small saucepan until it almost starts to boil.
2. Put the chopped chocolate in a bowl and add the hot cream. Let it stand for 1 minute and whisk it to combine well.
3. Whisk until the chocolate has completely dissolved and the mixture is smooth. 
4. Let cool until it has a spreading consistency. Spread small amounts over the cooled cookies and add sprinkles if you want to.
5. Keep covered and refrigerated if making it in advance.