Heat oven to 400˚F
Spread the potato cubes evenly on a baking sheet, and drizzle with olive oil and roast for 20 minutes.
Potatoes should be a bit under cooked, not yet tender
Melt the butter in a heavy pot over medium heat
Add onion, celery, sugar, and apple and sauté until soft
Add the garlic, cinnamon sticks, nutmeg, and thyme and sauté for 2 minutes
Add the chicken stock, potatoes, salt, and pepper and bring to a boil
Reduce heat and simmer uncovered about 15 minutes, or until potatoes are completely tender
Puree the soup in the pot using an immersion blender (or in a blender working in batches) until smooth
Add the maple syrup and whisk in the cream over medium-low heat, until warm throughout
Season to your liking
Add water or simmer for a bit longer until soup reaches desired consistency
Ladle into bowls and garnish with sour cream or crème fraîche