Heat oil on medium heat in a stock pot. Add the onions and sweat them until they are translucent. Add garlic and cook lightly. Do not brown onion and garlic.
Stir in the flour and mix thoroughly to make a smooth roux. Add the stock all at once and stir to combine.
Add carrots and turnip; increase heat to bring liquid to a low boil, stirring frequently to prevent burning. Reduce heat and cook until carrots and turnip are soft, about 15 minutes.
Stir in pumpkin, yogurt, spices, salt and pepper. Cook until pumpkin and milk are hot. Add more liquid if desired.
Process with a hand held blender (or put in blender or food processor), making a smooth puree. Taste and adjust the seasonings as needed.
Pour into serving bowls, garnish with seeds, sour cream/yogurt and/or a drizzle of maple syrup. Sprinkle with freshly grated nutmeg.