Boil the potatoes, peel them and leave them to cool overnight in the fridge.
Melt the sugar slowly in a large, heavy-based frying pan over a medium heat until you have a light golden caramel.
Add 50 g butter. Let the butter melt and brown whilst stirring the caramel.
Add the potatoes to the pan. Add a little sea salt and toss or swirl the potatoes around until the caramel has dissolved and forms a fine coating on the potatoes; this will take about 20 minutes. The caramel will harden initially on contact with the cold potatoes, but will melt once everything is thoroughly heated through. Remember to be patient! Turn down the heat so that it simmers gently and the caramel slowly thickens around the potatoes; stir or toss the potatoes in the pan as you go.
If the caramel seems thin, continue to cook/caramelise the potatoes until more water has evaporated from them.
