Mix the yeast with milk and sugar. Gradually mix in flour. Cover dough and let rise for 20 minutes.
Meanwhile, drain currants and dry on a kitchen towel.
Knead the whole eggs, salt, cinnamon and butter into the flour to form a pliable dough. Add the currants at the end.
Transfer dough into a greased round cake tin and cover. Leave to rise for 60 to 90 minutes.
Preheat oven to 200 C / Gas 6. Using a very sharp knife, slit an x-shape into the bread and brush beaten egg yolk. Bake for 1 hour until the top is golden brown. Remove from tin and let cool on wire rack.
Can be purchased from bakeries that make and bake their own bread. If unavailable, use 2 (7g) sachets dried active baking yeast.