If cooking chicken sous vide: pat-dry, season with 5 grams of salt, place in a vacuum sealed bag cook at 68°C for 1 hour.
If poaching chicken: bring enough salted water to cover the chicken to a boil in a medium pot. Turn off heat, place chicken in water, cover and wait for about 20 minutes. If you have a thermometer, check internal temperature is 74°C, otherwise check chicken is cooked in the middle.
While the chicken cooks, take the stems out of the Brussel sprouts, halve them and wash them. Place them on a baking tray lined with baking paper or tin foil. Bake until the halves are browned and the loose leafs are nice and crunchy. Set aside to cool down.
Let chicken cool down, then chop into bite size pieces.
Wash and slice celery stalks.
Toast hazelnuts in a dry pan until brown and fragant. Be careful not to burn them. Set aside to cool.
Dice avocado.
Mix chicken, Brussel sprouts, celery, avocado and cranberries. Season with lemon juice, salt and pepper. Serve and top with hazelnuts.