Pumpkin seeds are available at many supermarkets and at natural foods stores and Latin markets. The pumpkin seed oil can be found at specialty foods stores and at surfasonline.com.
03Working in batches, puree soup in blender until very smooth. Return to pot. Rewarm soup, adding more broth by 1/4 cupfuls if needed to thin. Stir in cream and season to taste with salt and white pepper. do ahead Can be made 1 day ahead. Cool, cover, and chill. Rewarm before continuing. Divide soup among bowls and garnish with toasted pumpkin seeds; top with a drizzle of pumpkin seed oil and some sautéed mushrooms, if desired.
04Tubers of a variety of sunflower; available in the produce section of some supermarkets and at farmers' markets.