In a small saucepan heat up the vegetable stock or bouillon and bring to boil.
If using large asparagus, blanch them in the stock (with the tips out of the water) until you can easily pierce the stalk with a knife (5-10 minutes). Remove them from the stock and turn down the heat to keep it warm.
Slice the asparagus (leaving the tips full) and sauté in a large pan with a knob of butter, until they start to brown. Season with salt and pepper, then remove from heat. Keep the tips and few of the slices aside for later and blend the remaining asparagus in a mixer with the heavy cream, until you get a creamy sauce.
In the same pan, add the rice and minced onion, and toast at high heat for 2-3 minutes. Add the white wine and let it evaporate for a couple of minutes.
Turn down the heat to medium-low and add some of the vegetable stock, until the rice is covered. Add more stock once the liquid is absorbed.
After 10 minutes, add the asparagus cream to the rice and keep cooking for another 8-10 minutes, adding more stock or water when necessary.
When the rice is cooked (al dente), add the grated Parmesan cheese, another knob of butter and mix well. The risotto should have a creamy consistency, not too stiff and not too loose.
Serve immediately, decorating with the asparagus tips you set aside.
Notes
If the asparagus are long, you may need to remove the tough ends. To do so, hold the asparagus with both hands and snap it in two. It will naturally snap where at the softer point, removing the woody part.