Hagrid's rock cakes from Harry Potter are delicious small fruit cakes. They are hard from the outside. Thus, they are called rock cakes. They are actually pretty easy to make.
First, leave the oven to preheat 375℉ while you make the dough.
Then, in the bowl of your stand mixer, add the flour, salt, and baking powder and mix. After that, add the butter and mix it until the flour becomes lumpy as the butter gets mixed with the dry mixture.
Add the raisins to the mixture and mix a little. Then, add the egg and the vanilla extract. Keep mixing until the dough just holds together. Add a few drops of milk so that it doesn’t feel too dry.
Use your hands to shape this dough into balls and place the dough balls on the baking sheet, and pop the sheet in the oven.