1. Melt butter in a pan, add white flour, cook lightly and remove pan from heat.
2. After 5 minutes add milk, put back on low heat and stir with a wooden spoon till it thickens.
3. Add salt and remove from heat.
4. In another pan heat the chicken and chicken stock for five minutes and add to the with sauce.
5. Add mushrooms, black pepper and cream before serving.
6. Serve hot with rolls and butter.