1. Peel the onion and potatoes
2. Using a food processor slice the onions as thinly as possible
3. In a pan cook the onions for 20 minutes using a little of the margarine until they are soft and sweet
4. Slice the potatoes using the food processor as thinly as possible
5. Line a deep tray with parchment paper
6. Melt the remaining margarine
7. In a suitable container (such as a pan) mix together the potatoes and margarine and season with salt and pepper
8. Arrange some of the potatoes in an overlapping layer (this will be the presentation side) then layer in the potato mixture and fried onions until the dish is full
9. Push the potatoes firmly into the bottom and corners of the dish, cover with parchment paper and then tin foil
10. Cook in a pre-heated oven at 170˚C for 1 hour or until the potatoes are cooked through
11. Allow to cool slightly then using something heavy such as a couple of large tins, press the potato cake
12. Once cooled cut into squares and serve hot with the Cawl

Milk