Melt 25g butter in a saucepan and cook mushrooms over a moderate heat for a few minutes until soft. Spoon out and set aside for later.
In the empty pan, for a quick all-in-one sauce, place all the sauce ingredients and bring to the boil over a medium heat, stirring all the time - ideally with a balloon whisk - until thickened.
Meanwhile, in a second pan, cook rice in boiling water for the time stated on the packet, usually about 10 minutes but depends on the brand.
Return the cooked mushrooms to the pan with the sauce and add the chicken. Stir to combine ingredients. Bring the mix to boiling point to ensure the chicken is thoroughly heated through and simmer for 5 minutes, stirring occasionally.
Drain rice and serve with a portion of chicken and mushrooms.
