Wash and peel the potatoes (or you could leave the skin on, if you like). cut them into thin slices.

Heat the butter and olive oil in a frying pan (it should have a close fitting lid of its own). add the onions and stir till they are a light brown.

Add the potatoes, and stir to coat with the oil. cook on a low heat, covered, for about 10 minutes, till the potatoes are soft.

Drain the potatoes in a colander and reserve the excess fat. let them cool.

In a large bowl, whisk the eggs with salt and a teaspoon of ice water.

Add the cooled potatoes to the eggs and mix well (the potatoes should be cooled to room temperature, otherwise they will curdle the eggs in the bowl).

Heat the oil in a non-stick frying pan, with a little bit of the reserved butter from the potatoes.

When the butter is melted and coats the base of the pan, add the egg mixture, make sure the potatoes are evenly distributed through the pan.

You can use a spatula to 'shape' the omletter's edges into a nice smooth shape.

Cover and cook on a very low heat for 3-5 minutes.

The center of the omlette should be just set, but a little wobbly.

Slide the omelette onto a plate, place the pan back on the heat. now hold the plate above the pan (exactly concentric with each other) and flip the plate over quickly, so that the omlette drops straight back into the pan, cooked side on top.

Cook the other side for about 2 minutes, till nice and golden brown.

Slide onto a serving plate. serve with garlic toast or croissants.