While the spaghetti is cooking, finely dice the onion and sauté in a pan in the oil of the anchovy fillets until translucent. Add the anchovies and stir until they ‘melt’.
Now reduce the heat a little.
Chop the garlic very finely and add it as well, stir briefly and mix the finely chopped pine nuts and parsley into the pesto and sauté. Season with pepper (the pesto is already salty enough from the anchovies) and add chili. Pour the pesto with 2 tablespoons of pasta water and mix with the dripping wet pasta directly from the pot. If you like, you can mix in half of the Parmesan before serving. The quantity makes 2 servings for very hungry people.