Add oil, butter, and pinch of salt & pepper to skillet. Turn stove to medium and warm until butter melts.
Chop onion and carrots, add to skillet and saute until they begin to soften. Do not cook completely, as they will continue to soften in the slow cooker.
Add onions, carrots, and all other ingredients to slow cooker, and set to medium. Stir well to mix in seasonings.
Put lid on slow cooker. Check after 1 hour, add seasonings to taste, then serve when ready.