Heat the stock and simmer. In a heavy based pan heat half the butter and all the oil. Add the shallot and cook until transparent. Add the dry rice and and stir until the rice is well cooked, then add the cleaned mushrooms,
Add 150ml of hot stock over the rice and cook stirring over a medium heat until the liquid has been almost absorbed. Continue adding the stock until the grains are swollen. Remove the pan from the heat and season to taste.