Meanwhile, in a food processor, grind walnuts until they are finally chopped.
In a large skillet, bring chicken or vegetable stock to a boil. Reduce to a simmer; stir in ground walnuts, cream and blue cheese. Season to taste with salt and pepper.
Boil pasta according to package instructions. Drain and add to sauce, tossing to coat.
Before serving, top each portion with a raw egg yolk and garnish with extra blue cheese and walnuts, if desired.