Apply a little salt and plenty of pepper to the meat and vacuum-seal it.
Cook it sous vide/water bath for 3 hours at 57 degrees Celsius (135 degrees Fahrenheit).
Remove the meat from the bag and dry it well - either with a tea towel or paper towels.
Heat a pan hard with neutral oil. When it's hot enough, add butter and brown the meat on both sides. It's now ready for serving.
The meat juice from the vacuum bag can be saved and used for sauces or stews.
Peel the potatoes and slice them as thinly as possible. We use a mandolin slicer for this.
Soak them in water for an hour and then dry them well with a tea towel.
The potatoes should be tossed in melted butter, fresh thyme, and pepper. Then, they should be stacked on top of each other in a round cookie cutter and baked in the oven for 1 hour at 200 degrees Celsius (392 degrees Fahrenheit).
Dice the vegetables into small cubes and cook them in milk and cream until they are tender in a heavy-bottomed pot. This typically takes 15-20 minutes depending on the size of the cubes.
Use a slotted spoon to remove the vegetables and place them in your blender/bowl for an immersion blender. Blend them with 1 dl of the liquid from the pot. Slowly add more of the liquid along with the butter and the liquid from the meat's vacuum bag.
Transfer it to a new, heavy-bottomed pot and warm it through over medium heat. Season it with salt, pepper, lemon juice, and vinegar.