Put into a pot, cover with water and simmer for 1 hour.
Strain, discard potatoes, reduce down liquid and season with salt.
Cut the potatoes into equal size pieces and seal in a vacuum bag.
Set the water bath on 72°C and cook the potatoes in the water for 45 minutes. Remove from bath and cool down bag in ice water. This cuts down the starch and the mash will not be sticky.
Cook the bag with pre-cooked bintje potatoes in boiling water until tender.
When cooked put the potatoes through a potato ricer to ensure equal size. Then place in a plastic container and keep until needed.
Heat egg yolks, milk, potato stock, sugar and invert sugar without boiling.
Add the riced potato and butter and stir together over heat.
Pass through a fine sieve and season with salt.
Spread the mash onto a silicon mat with a spatula to thickness of 2mm.
Freeze in deep freezer. When frozen, cut into thin long strips and keep in a container in a box
in the freezer until required.
Plum Stone Foam
Blend the peeled plum stones with the sugar and milk until smooth.
Pour into a vacuum bag and add the cream.
Seal and let it infuse overnight.
The next day strain and reserve liquid. The stones can be kept and reused.
Fill a siphon canister with the liquid and charge with 1 gas. Shake well and set aside in the fridge.
Wash the plums and dry off. Put in the oven and dehydrate at 60°C until they look like prunes. This will take about 10–12 hours.
Cook the flesh with aquavit and add the brown sugar when the alcohol has boiled off.
Cool down. Make sure that there are bits of prunes in the compote to give texture.
Hang the frozen plums in muslin and drain the juice off.
Cook the juice down to syrup.
Mix all together and keep cold.
Measure 15g of the plum compote and spread on a plate so that it isn't completely flat. Carefully, but quickly, place the batons on top of the compote so that they are vertical but not completely straight. Place the juice in between the gaps of the potato puree batons. Finish with a generous dollop of the plum stone foam off to the side.