Dice the onion, chop the garlic and ginger finely.
In a large pot, melt the butter over medium heat, add the onion, cook for about 7 minutes, stirring, until translucent.
Add the chopped garlic, ginger, and chestnuts, cook for a few minutes, stirring from time to time, until the butter turns golden brown.
Add the pumpkin puree or roasted pumpkin chunks and broth, cook over low heat, covered, for about 10-15 minutes.
Add the cream and take the pot off the heat. Puree the soup until smooth.
Season to taste with salt, black pepper, and lemon juice.
Serve with plain yogurt (can‘t be omitted! the soup is naturally sweet, yogurt needs to balance this sweetness), top with caramelized chestnuts and chopped and lightly toasted nuts.