Melt butter in a large saucepan, over medium heat. Add onion and let cook until translucent, about 10 minutes.Add flour and salt and mix well. Let cook for another two minutes.Add milk, half and half, chicken brother, and cauliflower and bring to a boil over medium high heat. Cover and reduce heat to low and let simmer for about ten minutes, until cauliflower is tender.Put soup in your Wolfgang Puck Commercial Blender and pulse until all the cauliflower is blended and soup is desired consistency.Place back in saucepan and heat until hot. Add mustard and cheeses and stir until the cheese is completely melted. Top with extra cheddar cheese and bacon bits, if desired.