Blanche the peas in boiling salted water for a minute, drain and refresh with cold water to avoid discolouring. Cook the pasta in the remaining water.  Reserve 1/3 of the peas aside and whizz the remaining together with the veg stock, herbs, lemon zest and juice, olive oil, garlic, salt and pepper, blend until smooth.  Drain the pasta and pour into a mixing bowl, stir in the spinach and mange tout, mix well to wilt the veggies with the heat from the pasta, stir in pea sauce and remaining peas, toss well. Serve sprinkled with feta crumbs and pine nuts.