Topping
Place the chopped carrot in a blender, also add the eggs and the oil, blend very well until combined, for about 2 minutes.
Transfer the batter to a bowl and add the refined sugar, mix well.
Gradually add the flour, sifting it through, to remove any lumps.
Mix well, gradually.
Grease a baking tin with butter and flour and pour this batter in it, spread evenly.
Bake in a preheated oven at 200°C (392°F) for 50 to 60 minutes (do the toothpick test).
Into a pan, add the sugar, the chocolate powder and the butter. Over medium heat, stir it all together until the butter fully melts (do not start making the topping of the cake before the cake has baked through).
Add the whole milk and mix nonstop until it thickens.
Pour the chocolate topping over the cake as soon as you turn off the heat, to keep it from getting hard.
Spread and serve.