To make risotto: Bring the vegetable stock to a boil in a medium saucepan, then reduce the heat and keep at a bare simmer.
2. Melt 6 tablespoons of the butter with the olive oil in a large, heavy saucepan over medium heat.
Add the onion and cook, stirring constantly with a wooden spoon, until softened and translucent, about 2 to 3 minutes.
Add the rice and cook, stirring, for about 3 minutes, until every grain is coated with butter and oil.
3. Add 1 cup of the stock and stir until the liquid is absorbed.
Continue adding stock, about 1/2 cup at a time, stirring frequently and making sure all the liquid is absorbed before adding more stock.
Cook until the rice is just tender and creamy but still al dente, 15 to 20 minutes.
You may have leftover stock.
4. To make pancetta: While risotto is cooking, cook pancetta in a medium skillet over medium to high heat until crisp.
Remove from pan and drain on paper towels.
5. To make lentils: Warm olive oil in a large saucepan over medium to high heat.
Add pancetta and cook for about 5 minutes, until crisp.
Add carrots, onion, and celery and cook for about 5 minutes, until softened.
Add wine and stir to deglaze the pan.
Add lentils, cover with water and bring to a boil over high heat.
Reduce heat and simmer until all water is absorbed, adding more water if needed, until the lentils have softened but are still al dente.
5. To make porcini mushrooms: Add olive oil, garlic, and porcini mushrooms to a large sauté pan and cook over high heat for 2 to 3 minutes.
6. To assemble: Just before removing risotto from heat, add the pancetta, lentils and porcini mushrooms; stir to mix evenly.
7. Remove risotto from heat and stir in the remaining 3 tablespoons butter and parmesan cheese.
Season with salt and pepper.