Preheat oven to 180ºC (355ºF). Place the flour and sugar in a bowl and mix to combine. Add the butter and use your fingertips to rub it into the flour mixture until it resembles fine breadcrumbs. Make a well in the centre and pour in the milk. Use a butter knife to gradually mix the milk into the flour mixture until just combined. Turn out onto a lightly floured surface and gently bring the dough together. Roll out to a 18cm x 24cm rectangle.
Sprinkle with the chocolate and roll up to enclose. Place in a 19cm x 9cm loaf tin lined with baking paper. Brush with extra milk and bake for 25–30 minutes or until cooked when tested with a skewer. Cool in the tin for 5 minutes and then turn out on to a wire rack to cool. Slice to serve. Serves 6–8.