In a large saucepan, heat the olive oil and butter over medium heat. Add the chopped onion and garlic, sauté until translucent.

Add the Arborio rice to the pan and stir for about 2 minutes until the rice is lightly toasted.

Pour in 1 cup of warm vegetable broth, stirring continuously until the liquid is mostly absorbed.

Continue adding the broth, one cup at a time, stirring frequently and allowing the liquid to absorb before adding more.

After about 15 minutes, add the asparagus pieces and continue cooking until the rice is creamy and al dente, about 5 more minutes.

Remove from heat and stir in the grated Parmesan cheese. Season with salt and pepper to taste.

Serve immediately, garnished with additional Parmesan if desired.