In a saucepan over medium heat bring broth to a simmer.
In a seperate saucepan or skillet combine oil and 1 tablespoon butter over medium heat.
Stir in onion and saute for 5 minutes. Add garlic and saute another minute.
Stir in rice, cook for 5 minutes, stirring to coat rice.
Add one cup broth; stirring constantly until absorbed. Continue to add broth by ladelfuls, stirring constantly, allowing each addition to be absorbed before adding more broth, until the rice is tender - this will take about 20 minutes.
Stir in asparagus during the last 5 minutes of cooking.
Remove from heat and stir in the Parmigiano and remaining 1 tablespoon butter and salt.
Divide among 4 bowls, topping each serving with Prosciutto.