Step 1

Pre-heat your sous vide machine to 60C. Vacuum pack the fish and place in sous vide when it is up to temperature. Set timer for 30 minutes

Step 2

Meanwhile prepare the rest of the ingredients

Step 3

Peel small onions and cook whole in salted boiling water until just cooked. If using chopped onions, cook them in the same way. Keep warm

Step 4

Chop the potato into cubes and place in boiling salted water to cook. This will be quite quick as they are small pieces. Check regularly and set aside when done. Keep warm

Step 5

Place the leek into 250ml milk and cook until soft. Drain and keep the milk for the sauce.

Step 6

Gently melt the butter, add the flour and cook a little, when it sizzles add the fish stock or milk and cook until thick. Add a little more milk or stock if necessary. Add salt and pepper to taste. Add the leeks to the sauce and chopped herbs.

Step 7

Now assemble the dish.

Step 8

Take the fish out of the sousvide, open and place on two warmed plates.

Step 9

Add the sauce to the dish. Add onions and potato. Place the fish on top.