Dice vegetables, apart from the peas and corn.
Melt butter in a pan or wok on fairly high heat and fry vegetables, apart from peas and corn, until browned and tender. Remove from heat and stir through peas and corn.
While the vegetables are frying, combine stock powder, couscous, and freshly boiled water in a heat-proof bowl. For minimal washing up, use the bowl you intend to serve the couscous in. Cover and leave to sit for 2-3 minutes, then fluff up with a fork.
Add vegetables and parsley to the couscous and serve.