Heat oil in a medium pot over medium heat. Add onion and cook for 5 minutes until translucent. Stir in the rice, spinach, broth, champagne, salt, and nutmeg.
Bring to a simmer and cook for 7 minutes. Stir in 1/4 cup cheese and the asparagus.
Pour the mixture into a pie dish and sprinkle with the remaining 1/4 cup of parmesan. Bake for 25-30 minutes or until liquid is almost absorbed.