Heat the oven to 400 degrees F. Peel the onion and finely chop it until you have two cups.
In a 5-quart pot, heat the olive oil on medium-high. Add the chopped onion and give it a stir to coat it with the oil. Let the onion cook for about five minutes or until tender.
Stir in the rice until it's combined. Then, stir in the spinach, stock, salt and pepper. Cover the pot and bring it to a simmer. When it starts to simmer, uncover the pot, lower the heat to medium-low, and cook the mixture for seven minutes.
While the pot is simmering, grate the Parmesan, if needed. (I throw chunks of cheese in my blender.) After the pot has simmered for seven minutes, stir in ½ cup of the Parmesan.
Transfer the rice mixture to a glass 9x13 pan. Cover the pan with foil and bake it for 10 minutes.
While the risotto is baking, rinse the asparagus and cut off the tough bottoms (cut off and discard the bottom two inches.) Cut the remaining stalks into 1-inch pieces.
After the risotto has baked for 10 minutes, stir in the asparagus pieces. Sprinkle the remaining ½ cup of Parmesan over the top. Cover the pan again and bake it for an additional 10 minutes. Taste it to see if it's done to your liking. If the rice seems too firm, bake it for an additional five minutes. Keep in mind, the risotto will soften as it sits.
Serve the risotto with red pepper flakes, additional Parmesan, and extra salt, if needed. Store leftovers in the refrigerator for up to four days, or freeze them. The risotto reheats well in the microwave.
Notes
Adapted from Cooking Light. I used stock instead of broth for more flavor, omitted the nutmeg, added pepper and doubled the recipe to make it in a 9x13. It serves 12 as a side dish or 8 as an entrée.If you want to make half of this recipe, you can use a Dutch oven from start to finish.In April 2024, I reduced the baking time for this recipe, since my newer oven cooks the rice more quickly. It now produces a firmer result instead of turning out mushy.