Peel the garlic and cut into wafer-thin slices. Heat 20 g fat in a pan. Sauté the garlic and prawns in it and let it cool down a bit. Clean and wash the tomatoes and cut them into thin slices. Mix mayonnaise, crème fraîche and lemon juice. Season with salt, pepper and sugar.
Spread the breads with the remaining fat. Cover with tomato slices and basil leaves. Spread mayonnaise on top and add the crabs. Sprinkle with pepper and garnish with basil. Serve the crab breads with lemon wedges