Preheat the oven to 180oc (160oc fan assisted)
Combine the flours and add the baking powder, mix through.
Peel and cube the potato and boil until soft, remove from the heat, drain and mash.
Cook the bacon in a frying pan with a little oil until it begins to crisp.
Chop the leek and add to the pan, cook until it becomes soft.
Combine the milk, butter and eggs and add to the flour, mix a little until it is combined but be careful not to mix beyond this point.
Chop the bacon into small pieces and add it to the mix along with the leek, potato, cheddar, parsley and pepper.
Mix the ingredients through but try not to overmix.
Spoon the mixture into greased muffin cases about 3/4 full.
Sprinkle each muffin with some walnuts and a little cheddar.
Place in the oven for 20-25 minutes.
Remove from the oven and allow to cool on a rack before serving, can be eaten warm or cold.