Toast the hazelnuts in the oven for about 8 minutes at 375°F/190°C. Let this cool completely.
Using a food processor, blend everything together except for the toasted hazelnuts. Don't overblend, just until a sauce is made.
Next add the cooled, toasted hazelnuts and pulse a couple of times to combine. The consistency of the pesto should spread nicely on toast.
Bring a large pot of heavily salted water to a boil. Cook the spaghetti according to package instructions or until al dente.
Add 6 tbsp of the pesto to a pan and allow to temper while the spaghetti cooks but don't heat directly. You can always add more pesto later if you want a stronger flavour.
Once the pasta is cooked, add to the pesto and toss. Add 1-2 ladles of hot pasta water until a nice sauce consistency is achieved. Serve right away and garnish with chopped toasted hazelnuts, fresh black pepper and a glug of olive oil on top. Enjoy!