Clean the truffles with a brush to remove any excess dirt. Finely chop the truffles (reserve a small piece for shaving on top).
Add ½ cup of olive oil and the anchovy to a small pot. Simmer on low heat and break up the anchovy with a small whisk. Add the chopped garlic and thyme and continue to simmer for 5 minutes. Add the chopped truffles and promptly remove from heat. Set off to the side and let cool.
Finely chop the shallot.
Remove sausage from casing. Heat 2 tablespoons of olive oil in medium skillet and add the sausage, and then break it up into small pieces. Sauté until golden brown. Add shallots and continue to sauté. Deglaze with vegetable stock and reduce slightly. Add the cooked truffles and season with salt and pepper.
Bring a large pot of salted water to a boil and cook spaghetti until al dente. Strain the spaghetti and add to the sauce. Add butter and the toss spaghetti over medium heat until it is a creamy consistency. Remove from heat and toss with grated Parmigiano. Finish with freshly grated black truffle.