Chop the onion and add to a large casserole dish with 1 tbsp of the olive oil. Cook gently for a couple of minutes, then stir in the risotto rice. Pour in the white wine and stir.
When the wine has mostly been absorbed by the rice, start adding the stock bit by bit, stirring all the time. Add more stock when the last bit has been absorbed. When you have added all of the stock, the rice should be just slightly al dente - taste it, if it's too al dente, add some more stock.
Roughly chop the asparagus, then add it along with the peas and spinach to the risotto. Stir well until the spinach has wilted, then turn off the heat. Drizzle over the remaining olive oil, sprinkle over the parmesan and put a lid on. Leave it for a couple of minutes.
Chop the feta into bitesize pieces, then stir into the risotto. Done!