In a medium saucepan melt butter.
2
Add onion, carrots, and celery, cook until tender. If you like a bisque-type of soup, puree it at this point with a stick blender, or in batches in a blender or food processor.
3
Stir in flour, cook and stir 2-3 minutes or until bubbly.
4
Stir in baking soda.
5
Gradually stir in milk, and broth, bring to a boil, reduce heat and simmer, stirring until mixture thickens slightly, about 10-15 minutes.
6
Add cheese, and red pepper, stirring until melted and well blended.
7
Garnish with parsley.