110g/3¾oz plain flour
2 tsp bicarbonate of soda
2 tsp soft dark brown sugar
1 tbsp black treacle or molasses
1 tsp salt
1 tsp sea salt flakes, plus extra if preferred
450g/1lb coarse wholemeal flour
butter, for greasing
300ml/10fl oz buttermilk
750ml/1¼ pint double cream (highest fat content possible), at room temperature
255ml/9fl oz Irish stout, such as Guinness
30g/1oz porridge oats, plus extra for sprinkling