Preheat your oven to 200°C (180°C fan) or 400°F. Line a baking tray with baking paper to prevent sticking and make cleanup easier. Measure out the ingredients, cut the cold butter into small cubes, and lightly beat the egg in a separate bowl. Preparing everything beforehand helps the dough come together without overmixing.

Place the self-raising flour in a large mixing bowl and stir in the caster sugar and optional mixed spice. Add the cold butter cubes and rub them into the flour using your fingertips until the mixture resembles coarse breadcrumbs. Work quickly so the butter stays cool. A few small buttery pieces are fine and can help give the finished rock cakes a tender, crumbly texture.

Stir the mixed dried fruit or raisins into the flour mixture until evenly distributed. If you enjoy a brighter flavor, add the optional lemon zest at this stage. Check that the fruit is separated rather than clumped together. Even distribution ensures that each rock cake contains a good balance of sweet fruit and buttery dough.

Add the beaten egg and mix gently with a fork or wooden spoon. Add milk one tablespoon at a time until the mixture forms a rough, slightly crumbly dough that holds together when pressed. Avoid adding too much liquid because rock cakes should not have the smooth consistency of cupcake batter. The dough should look uneven and rustic rather than soft and sticky.

Divide the dough into approximately 10 portions and place them on the prepared tray, leaving space between each mound. Use a spoon or your fingers to form rough, craggy shapes without smoothing the tops. Sprinkle with a little demerara sugar if desired. Bake for 15–20 minutes, until the cakes are lightly golden and cooked through. Smaller cakes may need less time, so check them near the end of baking.

Remove the tray from the oven and let the rock cakes rest for about five minutes before transferring them to a wire rack. Allow them to cool until warm or at room temperature. Their exterior will become slightly firmer as they cool, while the inside should remain tender and crumbly. Serve your freshly baked rock cakes with tea, coffee, or a glass of milk.