Cook the pasta according to the packet instruction. Add half of the peas to last minute of the cooking time. Drain, reserving about 1 cup of the cooking water.
Meanwhile put 1 cup of peas into a small food processor. Add the herbs, zest & juice of the lemon, oil and season to taste. Whizz for a few seconds until you get a coarse texture. Add the ricotta, mix well then taste. Adjust the seasoning and the lemon juice to your liking.
Toss the drained pasta & peas with the pea pesto and serve with grated Parmesan, freshly ground pepper and a few fresh herb leaves.