Melt the butter in a frying pan and fry the breadcrumbs until golden-brown and crisp.
Stir in half of the parsley, thyme, salt and freshly ground black pepper and mix until well combined.
Cook the spaghetti, according to packet instructions, in a large pot of salted water. Drain, mix with three tablespoons of the oil and set aside.
Meanwhile, heat a lidded frying pan and add the razor clams and half of the wine. Cover with a lid and cook for 2-3 minutes until all of the clams have opened.
Strain the razor clams and reserve the cooking liquid. Remove the razor clams from their shells and discard the intestine. Chop the razor clams and set aside.
Heat the remaining olive oil in the frying pan used to cook the razor clams and fry the chorizo for 2-3 minutes or until the oil is coloured. Add the uncooked clams, remaining white wine, garlic and chillies. Cover with a lid and cook for 3-4 minutes, or until the clams have opened. (Discard any clams that haven’t opened.)
Add the reserved chopped razor clams, reserved cooking liquor and cooked spaghetti. Mix until well combined. Stir in half of the parsley.
Season, to taste, with salt and freshly ground black pepper.
To serve, spoon the spaghetti into each of four serving bowls, spoon over any juices and sprinkle over the breadcrumbs.