Melt butter with oil in heavy large pot over medium heat. Add onion 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 spinach, cheese, sour cream and cayenne (spinach will wilt). Season with salt and pepper. Transfer dip to serving bowl. Serve warm with toasted baguette slices.
Stovetop
2000, 2001