Preheat the oven to 350 degrees F (175 degrees C). Butter a 6-inch round cake pan.
Place flour in a bowl. Rub butter into the flour until mixture resembles fine bread crumbs. Add mixed fruit, 1 cup plus 1 tablespoon sugar, and mixed spice. Stir to combine. Add milk and egg and mix until batter is soft and easy to drop.
Drop batter into the prepared pan. Sprinkle light brown sugar on top and pat down with the back of a spoon.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 1 to 1 1/4 hours.