As any shell fish the crabs have to be alive when you buy them. If you see them make thin bubbles, that means that they are hungry. So they have been around for a wild. When back in the kitchen wash them under running water. It is to remove any pieces of woods, seaweed etc… You can kill them by breaking their shell with a heavy knife or drop them in the large pot with hot olive oil. Make sure that the crabs line on the bottom of the pot so they die as quick as possible. During that time cut carrot, leek, onion, fennel in large dices. Remove the crabs when they are red and drop the vegetables. Stir them and let them roast for 10 minutes. Add thyme, basil, or lemongrass, star anise -your choice- Drop back the crabs on the top of the vegetables. Now it is up to you. You can add white wine -if that the case let it reduce by 2/3 before adding the other liquid-, water, chicken stock, fish stock etc… Bring to boil and start to remove the foam coming on the top of the pot. Add if you want coconut milk, almond milk, cream, depending on your mood. Let it simmer for 1 hour. For the thickener, corn, potato, sweet potato starch it is to you and your diet. The way I thick it it is to drop everything in the blender. I mean everything, vegetables, crabs. turn on the blender full blast and let it work its magic for 3-4 minutes and strain through a thin strainer. Repeat till done. Check the seasoning (salt, pepper, chili, lemon juice etc…) Enjoy as a soup, over a fish fillet, over pasta. Reduce to a thick sauce and add olive oil and lemon juice and it will become a great dressing for salads.