Peel the pumpkin and dice. Peel and chop the onion. Melt 1 tablespoon of butter , sauté the onion, add the pumpkin and fry for 3 minutes. Add potatoes and pour the vegetable broth, bring to a boil, salt and pepper, season with thyme, cook for 20 minutes. Mash soup into a puree and add the sour cream, cook for another 2-3 minutes. Dice the toast bread, melt the butter and fry the bread until golden brown, add the garlic. Pour the soup in plates and serve with croutons.