Take the time to make a good, rich homemade stock. A chicken carcass from last night's baked chicken, some celery, onions, carrots, a potato and tomato, some fresh parsley, thyme, sage, oregano and garlic as well as shiitake and porcini mushrooms in a couple of quarts of water will work beautifully when reduced down to 6 cups. This is very important because the key to a wonderful risotto rests upon the quality of its stock.
Bring a large pot of water to a boil and add one-fourth teaspoon salt. Drop the asparagus pieces into the boiling water for about one and one-half to two minutes; remove from the heat and drain in a colander and rinse under cool water. Don't overcook! Make sure they retain their bright green color.
Heat the olive oil and butter in a large heavy skillet and add the leeks, one-fourth teaspoon salt, and a few pinches of pepper. Cook, stirring, over medium heat for 3 to 4 minutes, until they begin to soften, then add the garlic and cook for another minute or two.
Add the rice and saffron and cook, stirring, for 2 to 3 minutes. Begin adding the stock, a cup at a time, allowing the rice to absorb each cup of stock completely before adding more. Keep stirring. This is where a high kitchen stool and a glass of wine come in handy.
When the rice has absorbed 3 cups of stock, add the wine and one-fourth teaspoon salt. Continue to add the stock, stirring constantly, until you have used five to five and one-half cups. As you stir in the last of the stock, add the asparagus, one-fourth teaspoon salt, and a few pinches of pepper. At this point the grains of rice will still be a little toothy, the risotto will be quite saucy, and it should be ready to serve. Stir in the Parmigiano-Reggiano and serve immediately.