"Getting your greens doesn't have to be boring!..."
extra-virgin olive oil
yellow onion, finely chopped
stalks celery, finely chopped
leek, cleaned and thinly sliced (white and pale green parts only)
cloves garlic, minced
thyme, freshly chopped
red pepper flakes (optional)
Kosher salt
Freshly ground black pepper
low-sodium vegetable broth
water
(15.5-oz.) cans cannellini beans, drained and rinsed
Juice of 1 lemon
large bunch kale, removed from stems and torn into medium pieces
Freshly grated Parmesan, for serving