Cook the spaghetti al dente, then drain (do not quench with water, otherwise the starch film will dissolve and the sauce will not be so well accepted). Save a cup of pasta water.
Peel the garlic and chop it finely or press it through a garlic press. In a saucepan, slowly heat the oil and butter with the garlic. Be careful not to get the garlic dark, otherwise it will turn bitter. Add the crabs or crayfish tails and sauté with them. Add the spaghetti and pour in the stored pasta water. Mix in the parsley and basil and toss everything through. Salt and season with a pepper mill if you like.
A fresh salad goes well with it.
Tip: Best to eat in pairs, otherwise the garlic smell is difficult to cope with.