1. Let the butter until golden in a pan and fry the fillet over a moderate heat for approx. 25 minutes. Measure with a meat thermometer meat core temperature. It should be approx. 55°C. Sprinkle the meat with salt and pepper and keep hot.
2. Bring water and nuts to a boil in a saucepan. Bring to the boil over a high heat for approx. 2 minutes. Let the nuts drain in a sieve.
3. Place the butter in a pan and fry the onions and oyster mushrooms for approx. 3 minutes, while stirring occasionally. Put nuts, broth, salt and pepper in the pan with the mushrooms with cream and Castello® Extra Creamy Danish Blue cheese. Remove pan from heat and add the sauce thickener.