Bring a large pot of water to a boil for the pasta.
Meanwhile, heat the EVOO over medium-high heat in a large skillet with tight-fitting lid. Add the sausage and brown and crumble. Add the onion, garlic, chili pepper and thyme; partially cover and soften for 5 minutes. Add the vermouth, stock and clams; cover and cook until the clams open. Discard any unopened clams.
Cook the pasta to al dente. Reserve half a mug of the starchy cooking water and drain.
Add the butter and parsley to the clams and season with salt and pepper. Add the pasta to the skillet and toss with the starchy cooking water to combine. Serve immediately.