In a large pot heat butter and olive oil on high. Add the onion, celery, garlic, thyme and bay leaf and cook for 2 to 3 minutes until soft. Add pumpkin and allow it to sweat until it just begins to lightly brown. Add the stock and white wine. Bring to a boil and simmer for 20 minutes or until pumpkin is very tender.
Remove and discard thyme bundle and bay leaf. Process cooked pumpkin in a blender to make puree. Pass purée through a fine-mesh sieve.
Return to puree to a pot and heat over medium heat, seasoning with salt and freshly ground white pepper. If soup is too thick, thin it with more stock. Reduce heat to low and keep warm.
In a small mixing bowl, whip the cream to soft peak stage. Add nutmeg and season with a pinch of salt.
To serve, ladle soup into 4 soup plates, and sprinkle with croutons and pumpkin seeds. Serve the cream in a small bowl at the table.