Peel the potatoes and put on to boil in salted water. While they are cooking, prepare the pancake batter by incorporating the beaten eggs into the flours and salt and adding enough milk until you have the consistency of thick cream. Allow to rest for 20 minutes or so. Before cooking add enough water to bring the consistency to one of thin cream.
Fry the onions and red pepper for a few minutes in
Cook the pancakes in the butter and oil on one side only. Flip over briefly to dry the other side but not take colour. Lay them out with the cooked side upwards and spread a quarter of the potato mixture onto each. Roll up and, seam side down first, fry in the butter and hot oil until browned on all sides.