Asparagus Risotto

1 1/2 pound asparagus, peeled, trimmed, and cut into one-inch-long pieces, tips reserved
6 cups vegetable stock
3 tablespoons extra virgin olive oil
4 1/2 tablespoons butter
1/2 medium red onion, diced
2 1/4 cups Arborio rice
3/4 cup dry white wine
Salt to taste
3/4 cup grated Parmesan cheese

1. Bring a pot of water to a boil, add half asparagus, and cook until soft (at least 5 min). Rinse under cold water and blend, adding cooking water as necessary to puree until smooth.

2. Warm stock. Put oil and 1 1/2 Tbs butter in a pot over medium heat. When it is hot, add onion, stirring occasionally until it softens, 3 to 5 minutes.

3. Add rice and cook, stirring occasionally, until it is glossy, about 2 to 3 minutes. Add white wine, stir, and let liquid bubble away. Add a large pinch of salt. Add warmed stock, 1/2 or so at a time, stirring occasionally. Each time stock has just about evaporated, add more.

4. After about 15 minutes, add the remaining asparagus pieces and tips, continue to add stock when necessary. In 5 minutes, begin tasting rice. You want it to be tender but with a bit of crunch; it could take as long as 30 minutes total to reach this stage. When it does, stir in 1/2 cup of asparagus puree. Remove skillet from heat, add the remaining butter, and stir briskly. Add Parmesan and stir briskly, then taste and adjust seasoning. Risotto should be slightly soupy. Serve immediately.