Cook the spaghetti in salted water (I prefer `al dente`), then drain.
Peel off the garlic cloves and puree or press them through a garlic press. In a pan, slowly heat 5 tablespoon chilli oil and half of the butter together with the garlic and the finely chopped chilli pepper on a low heat. Be careful not to burn the garlic or to make it too dark. Add the shrimp or crayfish tails and simmer slowly - still on a low level. After about 15 minutes, add the spaghetti. Add the remaining 5 tablespoons of chilli oil and the remaining butter. Carefully mix the spaghetti with the remaining ingredients and serve.
I serve with a green salad with a buttermilk and lemon dressing.