How to Make It
Heat the oil in a large saucepan. Add the onion, celery and half of the garlic and cook over moderate heat, stirring, until tender, 8 to 10 minutes. Add the tomato paste and cook, stirring, for 3 minutes. Stir in the tomatoes, thyme, marjoram and bay leaf, cover partially and simmer over low heat for 1 hour.
Heat a large skillet. Add the sausages and cook over moderate heat, stirring, until browned and cooked through, 8 to 10 minutes. Transfer the sausages to a dish.
In a large saucepan of boiling salted water, cook the pasta until al dente. Drain, rinse under cold running water and drain again.
In a large saucepan, heat the wine with the remaining garlic. Add the clams, cover and cook over moderately high heat until they open, 4 to 5 minutes. Using a slotted spoon, transfer the clams to a bowl and let cool, then remove the clams from their shells. Strain the cooking liquid, leaving behind any grit.
Reheat the tomato sauce in a large saucepan. Add the sausages and cook over moderate heat until warmed through, about 5 minutes. Stir in the pasta, clam liquid and crushed red pepper and reheat thoroughly, about 8 minutes. Add the clams and season with salt and black pepper. Sprinkle with the parsley and serve.