Process flour, eggs, and egg yolks in a food processor for one minute until dough forms.
Wrap dough in cling film and chill in the refrigerator for 30 minutes.
Roll half of the chilled dough through a pasta machine to the thinnest setting and dust with semolina.
Combine ricotta and chopped fennel in a bowl and season with salt and pepper.
Place teaspoons of filling along the pasta sheet with 3cm gaps between each portion.
Moisten the pasta between fillings with water and fold the dough over to cover.
Press down around the filling to seal, ensuring no air is trapped inside.
Cut the pasta into half-moon shapes using a round pastry cutter.
Crush garlic with salt in a mortar, add walnuts and pound until smooth, then mix in lemon, cheese, milk, oil, and parsley.
Whisk the sauce until emulsified and season to taste.
Boil the pasta in a large pan of salted water for 3 to 4 minutes.
Melt butter in a frying pan, then toss the drained pasta to coat.
Stir in a spoonful of walnut sauce and serve with extra sauce and black pepper.