Heat a heavy gauge 6-quart saucepot over medium-high heat until hot. Add olive oil, onion, carrots, and celery; cook for 5 minutes or until vegetables have softened slightly, stirring occasionally. Add garlic and cook for 3 minutes. Add Brussels sprouts, sweet potatoes and thyme; cook for 8 minutes, stirring occasionally.
Heat cream in a medium saucepan over medium-low heat 5 minutes or until warm so as not to curdle when added to the hot sweet potato mixture.
Stir wine into sweet potato mixture, then stir in chicken stock and warmed heavy cream. Heat to a boil. Reduce heat to low and simmer for 30 minutes. Stir in sherry, salt, pepper and nutmeg. With stick blender, purée soup until smooth.
For the Brussels Sprouts Crisps Garnish
Deep fry shaved Brussels sprouts for 30 seconds; drain and toss with salt and pepper.
Ladle soup into bowl and drizzle with the pumpkin seed oil. Add Brussels sprouts crisps garnish and sprinkle with toasted pumpkin seeds.