Clean the greens by soaking them in water and spinning them with a salad spinner. Remove any stalky stems and chop roughly and set aside.
In a large skillet or Dutch oven, heat the olive oil over low heat. Peel and smash the garlic. Add it to the oil and let it infuse into the olive oil over low heat for 1 minute, being careful it does not burn. Add the red pepper flakes and let cook for another minute or so.
Add the greens (you may need to do this in batches depending on the size of your pan) and a generous pinch of salt and gently cook until wilted, anywhere from 2-5 minutes.
Add the cannellini beans, 1 ½ cups of broth (or bean cooking liquid), the parmesan rind, if using, and plenty of freshly ground black pepper, and combine. Bring the Italian greens and beans up to a boil, turn down the heat to low and simmer gently until the broth has thickened, anywhere from 8-12 minutes, stirring periodically. While cooking, smash some of the cannellini beans with the back of a wooden spoon or fork, which will create a creamy texture. If it seems to dry, add another ½ cup of broth. Remove the garlic cloves.
Remove from the heat and squeeze in the lemon juice. Test for seasoning (this will depend on the type of broth you used and its sodium content) and season with salt and pepper accordingly.
Serve with crusty bread, parmesan cheese, if you like and a hefty guzzle of extra virgin olive oil.