Start by boiling the stock, then lower the heat and keep it simmering while you cook your risotto.
Place a deep 24-cm pan (about 2 liters) over medium-high heat.
Pour the oil and once it's ready, add the chopped onion --- and saute until it softens.
Add the rice. (NOTE: Do NOT rinse it!) Stir (toast) the rice for about 2 minutes, making sure that the grains are coated with oil.
Pour the white wine.
Stir and let it evaporate --- at this point, you will see the creaminess coming out of the rice.
Add 2 to 3 ladles of the simmering stock. Keep stirring until most of the liquid has disappeared, then add a couple more ladles of stock.
After about 5 minutes of cooking, add the hard parts of the asparagus --- continue stirring and adding stock.
After another 5 minutes, add the chopped asparagus tips.
Continue stirring and adding the stock for about 10 more minutes, or until the rice is cooked --- still with a bit of bite left.
Taste and adjust the seasoning by adding salt.
Before turning off the heat, check that you have enough liquid left.
Do this by gliding your spatula from one side of the pan to the center; you should see the liquid part, then slowly converge --- almost like a wave.
Turn the heat off and add the chilled butter and grated cheese. Mix a bit to combine, cover with a lid, then remove the pan from the stove --- let it sit for 2 minutes.
Transfer your asparagus risotto to plates.
Top with more grated Parmigiano Reggiano --- serve and enjoy!