Peel the pumpkin, remove the seeds and cut into cubes. Peel and finely dice the onions. Heat 30 g fat in a pot and fry onions and pumpkin in it. Deglaze with the broth, bring to the boil and cook for 30 minutes.
Puree the pumpkin in the broth with the cutting stick of the hand mixer. Add cream and season to taste with salt, pepper, Tabasco and nutmeg. Rinse crabs briefly and dab dry with kitchen paper. Peel garlic and dice finely.
Heat the remaining fat in a frying pan. Sauté garlic and prawns in it. Add to the soup before serving. Dust with pepper.