Scald 225ml milk, and combine with 100g sugar and 100g butter. Set aside to cool.
Add eggs, vanilla and pinch of salt to cooled milk mixture. Mix together. Add yeast mixture. Gradually add flour and sultanas until dough comes away from the bowl. Knead the dough until pliable. Avoid handling the dough more than necessary! Place dough in a well oiled bowl. Set aside to rise until doubled in size in a draught free area.
Combine 475ml cold milk, remaining sugar and pinch of salt in a saucepan. Stir in rice and bring to the boil. Add 15g butter. Lower heat, cover and cook for about 20 minutes until done. Set aside to cool.
Punch down the dough, and knead a couple of times. Place into the centre of a lightly greased and floured casserole or deep sided cake tin. Spread dough by patting gently to all sides. Let rise for 15 minutes.
Spread rice mixture on top of dough and pull sides up gently to form an envelope design. Rice will show in centre. Brush the top lightly with melted butter and sprinkle with cinnamon.
Place in a preheated 190 C / Gas mark 5 oven for 10 minutes. Lower temperature to 180 C / Gas mark 4. Bake for an additional 30 minutes or until golden brown and cooked through.