In a large sauce pan, melt butter over medium heat. When melted, stir in the flour until mixture clumps up. Very gradually whisk in the milk until all milk has been added and a thick white sauce forms.Add chopped onions, broccoli, garlic, Italian seasoning, and cream cheese to your slow cooker. Add the sauce from the pan, and the chicken broth. Stir to combine. Cover and cook on high for 3-4 hours or on low for 4-6 hours.Uncover soup and add the sharp cheddar cheese, salt, and pepper. Stir until the cheese melts into the soup. Taste and add salt and pepper if needed. Serve warm and top with additional shredded cheese if desired. Enjoy!