This slow cooker bolognese is a hearty and flavorful dish that is packed with hidden vegetables. The sauce is made with a combination of ground beef, onions, carrots, celery, and tomatoes, which are cooked low and slow to develop rich flavors. The vegetables are finely chopped and blend seamlessly into the sauce, making it a great way to sneak in some extra nutrients. Serve this bolognese over pasta or use it as a filling for lasagna or stuffed peppers.