Risotto for two last night. This recipe has the basic technique.
After softening the onion, this time with half a clove of garlic (I added a splash of water every so often to prevent the vegetables from catching, and used a heat disperser under the pan for the last 10 minutes of the 25-minute process), I stirred in the rice, and then added chopped (quite small pieces) mushrooms -- three portobellos. I got everything hot, before adding the stock, ladleful-by-ladleful as usual.
Green vegetables should go into a risotto at the end, so that they retain their freshness. Mushrooms can be there from the beginning, contributing their flavour to the sauce. The disadvantage is that you get a risotto that is a sludgy, grey-brown. If appearance matters, saute the mushrooms apart, and stir them in when the rice is ready.
Parmesan is what you should stir into a risotto. But I fancied a milder flavour. When the rice was al dente, I took it off the heat, adding the peas and about 100 g (I should guess) of grated Gruyere, along with 20 g of butter, cubed and chilled.