Season, roll (from the tail end and skin side out) and skewer each fillet.
Bring a third of a pan of water to the boil in a medium sized saucepan. Add the saffron, turmeric and potatoes and cook with the lid on. After seven minutes remove the lid and place a sieve on top of the pan and put the kale in the sieve, replace the lid and cook both for a further three minutes.
In a separate small saucepan add the stock, wine and bay leaf and bring to the boil. Place the sole in the pan resting the skewer diagonally inside ensuring it is above the water line. Cook with the lid on for roughly three minutes.
When the potatoes are cooked turn off the heat, remove them from the water and place in the sieve with the kale. Remove the fish from the small pan when cooked and add to the sieve with the potatoes and kale and cover.
Return to the small saucepan, ensure the poaching liquor has reduced to about two tablespoons and add the butter a cube at a time whilst continuously whisking. Carry on until your sauce is thick enough to coat the back of a spoon.
Season the vegetables and present them alongside the fish, drizzle the sauce over the fish.