200g/7oz long-stemmed broccoli, trimmed and each stalk cut into three pieces
1 small lemon, finely grated zest only
240g/8½oz whole wheat penne pasta
salt and freshly ground black pepper
175g/7oz reduced-fat crème fraîche
25g/1oz Parmesan, finely grated, plus extra for serving
100g/3½oz frozen peas