Peel the potatoes and chop into 1cm cubes, trim and slice the spring onions, then place in a large non-stick frying pan on a high heat with 2 tablespoons of olive oil and 250ml of boiling kettle water. Reduce to a simmer, then cover and cook for 15 minutes, or until the potatoes are just tender, adding the peas for the last 5 minutes, stirring occasionally. Meanwhile, cook the pasta in a pan of boiling salted water according to the packet instructions, then drain, reserving a mugful of starchy cooking water. Tip the drained pasta into the pea and potato pan, finely grate in the pecorino, then toss together, adding splashes of cooking water to loosen, if needed. Season to perfection, and finish with an extra grating of pecorino and a drizzle of extra virgin olive oil, if you like.