Add first ingredients to a slow-cooker, and carefully stir to combine. Cook on low heat for 6-8 hours until the vegetables are tender. Remove bay leaf, and carefully stir in the kale. Let the stew continue cooking for 10 minutes or so until the kale is wilted. Season with additional salt and pepper if need be. Turn off slow cooker.
Serve immediately, with the option to garnish with fried sage leaves or Parmesan cheese.
To make the fried sage leaves, heat 1/4 cup of vegetable or canola oil in a small skillet over medium-high heat until a drop of water sizzles on the surface. Add your sage leaves and let them cook for about 10 seconds, then remove with a slotted spoon and place on paper towels to drain.
Sprinkle with a pinch of salt if desired.