Place the broccoli, cauliflower, carrot, shallot, garlic, salt, pepper, hot sauce and vegetable or chicken broth in the slow cooker. Stir everything together then cover with the lid and set to low. Cook for 6-8 hours or until the vegetables are very tender. Use an immersion stick blender or regular blender to purée the soup until it's smooth. Add in the milk and cheese and blend until the cheese is melted and everything is combined. Blend in the Greek yogurt until combined and the soup is smooth. Taste for seasoning then serve. Serving size 4-6