Drop the nuts in to a small pan of boiling water, and cook for 1-2 minutes. Drain. Slip off the skins. Dry on paper towels. Coarsley chop and set aside about a quarter of the nuts.
Place the remaining nuts, the breadcrumbs, oil, parsley and garlic, if using, in a food processor or blender. Process to a paste. Remove to a bowl and stir in the softened butter and the cream. Season with salt and pepper.
Cook the pasta in a large pan of rapidly boiling slated water until al dente. Drain, and toss with the sauce. Sprinkle with the reserved chopped nuts, and pass the Parmesan separately.