1 Put the vegetable stock on to boil. (You can use water instead of stock at a push.) Keeping a handful of raw peas to one side, cook the rest in the boiling stock for five to seven minutes, depending on their size. While the peas cook, boil the pappardelle for seven or eight minutes in generously salted water.
2 Put the peas and 150ml of their cooking liquor into a blender and process until smooth, introducing more stock as necessary to produce a thin, brightly flavoured sauce. Drain the pasta and return to the pan, pour in the pea sauce, scatter with the Parmesan and fold in. Check the seasoning. Divide between two deep plates.
3 Break the sheep's cheese into large pieces, scatter over the pasta with the reserved raw peas and serve.