Melt butter in heavy large pot over medium heat. Add onion, shallot and garlic; saute until onion is tender, about 6 minutes.
Add flour; stir 2 minutes. Gradually whisk in stock and cream; bring to boil, whisking constantly. Cook until mixture thickens, stirring frequently, about 2 minutes. Remove from heat.
Stir in fresh organic spinach, parmesan cheese, and sour cream. Add cayenne (spinach will wilt). Season with salt and pepper. Transfer dip to serving bowl. Serve warm with toasted baguette slices. Enjoy!