Cut the onions into small cubes, finely chop the garlic. Trim the wooden ends of the asparagus then cut it into 1-inch (2.5cm) pieces.
Warm up the broth until it's hot, keep the pot with the broth on the stove over the lowest setting, it should stay hot while the risotto is cooking.
Heat the oil in a large pot over medium heat, add the onions and cook for about 4-5 minutes or until soft.
Add the garlic and thyme, cook for 30 seconds.
Add the rice, cook for a couple of minutes, stirring from time to time until all the grains are covered in oil and translucent at the edges.
Add the wine and cook until it's evaporated.
Add the broth, about 1/2 cup at a time. Add the first half of a cup of broth, push the rice grains with a spoon, so that all the rice is submerged under the broth. Cook for 1-2 minutes until the rice has absorbed the broth that was above the rice. Now stir the rice with a spatula and cook, stirring until there's no broth in the pot and the rice starts to stick to the bottom of the pot. Add another 1/2 cup of broth and cook as described before.
After about 25 minutes add the asparagus, and cook (adding broth as described above) for about 5-10 minutes until it's tender but still crunchy. The rice should be cooked al dente at this point (it should be soft but still have a little bit of bite to it), if it's not soft, cook it a little bit longer.
Add the peas, parmesan cheese, cream, lemon zest and juice, cook for a minute.
Season the risotto with salt and pepper to taste.
Serve sprinkled with more parmesan cheese and thyme leaves.