Pour the warm water into a small mixing bowl and soak the dried porcini mushrooms for about 20 minutes.
After the 20 minutes, remove the porcini mushrooms from the water and chop them coarsely. Set aside.
Pour the water from the mushrooms through a cheese cloth filter into a small saucepan. Place the saucepan on the stove and keep it at a simmer.
Place the beef broth in a separate saucepan and place it on the stove, also at a simmer.
Put a large stock pot over a medium flame and add the onion, the extra virgin olive oil and the butter. Sauté and add salt and pepper as desired.
Once the onion turns soft, about 3-5 minutes add the porcini mushrooms to the pan. Sauté the mushrooms for 3-4 minutes and add the arborio rice.
Toast the rice for 3-4 minutes and add the white wine.
Once the alcohol from the wine has evaporated stir in about 1 cup of hot porcini broth. Continuously stir the rice until the broth is absorbed.
Continue alternating adding porcini broth and beef broth a little at the time while you are stirring until the rice is al dente. This will take about 20 minutes.
Once the rice is to your desired consistency remove the pot from heat add in the grated parmigiano. Stir and pour in a large bowl. Garnish with more grated parmigiano.