In a large heavy pot saute the pancetta in 1 tablespoon of olive oil for 7-10 minutes over medium heat or until the pancetta has rendered most of its fat.
Next, add in the onions and saute for 5 minutes then add in the garlic and cook for 1-2 minutes more until just golden. Finally, add the hot red pepper flakes and cook for 30 seconds.
Next, add in 6 cups of water, 1 teaspoon of kosher salt, and the plum tomatoes and give it all a stir. Add in the drained beans, the rosemary if using, and the Parmigiano Reggiano rind (if you don’t have one, you can use a bit of grated cheese or just omit) and bring to a boil for 5 minutes.
Lower the heat to medium and crush some of the beans by smashing them against the side of the pot with a wooden spoon. For a creamier consistency use an immersion blender, or spoon 1/3 of the beans into a regular blender and pulse. If using an immersion blender, remove the rosemary sprig and parm rind before blending. Don't blend too much so that some of the whole bean texture is maintained. Make sure to do this step before adding the pasta!
Add in the pasta and cook until al dente. Keep an eye on the pot and stir very frequently to avoid sticking. The pasta will absorb much of the liquid so add more water as needed. The final consistency of the pasta e fagioli is 100% a personal preference. If you like it soupier, add more water!
Once the pasta is al dente turn off the heat and taste test. Adjust salt (will probably need a good amount), pepper, and hot red pepper to taste.
When satisfied with the taste, serve in bowls with crusty bread. Offer grated cheese, hot red pepper flakes, or black pepper on the side and drizzle some high-quality extra virgin olive onto each bowl. Enjoy!