In a medium Dutch oven, combine the white beans, sage, garlic, 2 tablespoons olive oil and 6 cups water (bottled preferred). Bring to a boil over medium-high heat, then reduce the heat to medium-low to maintain a gentle simmer. Cook, partially covered, for 1 hour 20 minutes, stirring occasionally; the beans should be just tender all the way through.
Add the kale, salt and red pepper flakes to the beans and stir to combine. Cover the pan and simmer until the kale is wilted and tender, an additional 15 minutes. Stir in the remaining 1/2 cup olive oil and the cheese to finish.