Cook the eegs in boiling water for about 6 minutes, then drain and run under cold water. Remove from the shells and cut into thick slices.
Peel and cook the potatoes until soft, then mash until smooth.
Grate the cheese for the sauce.
Melt the margarine in a pan, the add the flour and cook until sandy in colour and texture. Add the milk gradually, whisking all the time. Continue to cook until the sauce thickens, then add the cheese.
In a deep tin, put a layer of mashed potato then a layer of sliced egg, continue until you finish with a layer of potato.
Pour over the cheese sauce and cook for 20 minutes until golden brown.