Mix the flour, salt and baking soda in a bowl and make a well in the centre. Add the buttermilk and oil and mix to a dough. Place on a floured surface and roll out to a centimetre thick.

Cook until soft, then blend to a smooth puree. Cook the bacon until crisp and golden. Place on kitchen paper and wilt the scallions in the fat. Cut 8 slices of the bread and spread mayonnaise and ...