Braise the onions and garlic in the olive oil and butter in a large pan. Add the chicken meat that's been chopped into bites and braise them until golden. Add the chopped mushrooms and cook another 5 min.
Pour in half a cup of the broth and cook until the liquid gets absorbed. Keep adding 1/2 cup of broth at a time until the rice softens.
Season the risotto with salt and grated parmesan, stir and remove from the stove.