Preheat your oven to 375°F (190°C) and line a baking tray with parchment paper.
In a large bowl, mix the flour, baking powder, salt, sugar, and pumpkin pie spice together until well combined.
Cut the butter into small cubes and rub it into the dry ingredients with your fingertips. Keep going until the mixture looks like coarse crumbs.
Stir in the currants so they are evenly spread throughout the mixture.
Beat the egg with the milk, then pour this into the bowl. Mix everything gently with a spoon or your hands until it forms a soft, sticky dough. Add a little more milk if it feels too dry.
Dust your hands and the work surface with flour. Take spoonfuls of dough and shape them roughly into small, uneven mounds—this gives the rock cakes their signature look. Place them on the prepared baking tray, leaving space between each cake.
Sprinkle some sugar over the tops for a sweet, crunchy finish.
Bake for 15-18 minutes or until the cakes are golden and firm to the touch.
Remove the rock cakes from the oven and let them cool slightly on a wire rack before enjoying.