Dice the onion and saute in 1 or 2 tablespoons of olive oil. Now slice the garlic thinly.
When the onion is translucent, add garlic and mushrooms.
When the garlic begins to brown or after a couple of minutes, add the wine and reduce.
When the wine is reduced by half, add the greens. It helps if you don't get them completely dry after washing; this will give them some water to steam in. Stir well and cover.
After about five minutes, check them for crispness - they should be slightly wilted, but still bright green.
Add the white beans and cover again. Its all ready once they are warmed through then season with salt and black pepper or chile flakes.
*If you're using very strong greens, like mustard greens or something like that, you will want to boil them first separately. Then you can add them and the beans at the same time.