Preheat the oven to 180 ° C top / bottom heat. Line a muffin tin with paper liners.
In a large bowl, stir together the vegetable oil, sugar and eggs until creamy. In a second bowl, mix the flour, salt, vanilla sugar, cocoa powder, cinnamon and baking powder together. Carefully stir in the flour mixture alternately with the milk. Spread the dough in the molds and bake for 20-25 minutes. Make a chopstick test. Let cool down completely.
Mix the butter and sugar until creamy. Stir in the salt and vanilla sugar. Stir in the flour with the milk. The frosting should be as soft and sticky as American cookie dough, it shouldn`t be malleable like shortcrust pastry. If necessary stir in more milk. Stir in the chocolate chips.
Pour the frosting into a piping bag with a large nozzle and distribute it on the cupcakes. Refrigerate.
Tip: The frosting can also be spread over the cupcakes with a small ice cream scoop or a spoon.