Thinly slice potatoes 1 centimeter thick and place in layers in roasting tin, seasoning each layer with salt and pepper.
In a saucepan melt the butter and pour over the potato layers.
Place another tin over the layers and compress, cook in the oven at 160 degrees for 40 minutes.
Once cooked chill in the fridge for an hour until firm.
Remove from the tin and cut into 2x5 centimeters rectangles.
Deep fry until golden brown and crispy.
For the Tarragon Mayonnaise
Drape a cloth over a saucepan and place bowl on top (for support).
In the bowl 2 egg yolks, tablespoon spoon of English mustard, 3 grams of salt and 1 gram of white pepper, whisk until fluffy and slowly add sunflower oil, keep whisking until mayonnaise consistency.
