Melt butter. Saute bacon, then add onion, leek, and celery. Cook until heated through. Add flour and stir until well combined. Stir in stock; simmer for 15 minutes. Add broccoli; simmer for 15 minutes. Pour into blender and puree. Return to pan and season with salt, pepper, and nutmeg. Stir in cream and cook until heated, do not boil.