Put the couscous into a bowl, pour vegetable stock over it, cover and set aside.
In a food processor, whizz up the basil, pine nuts, and harissa paste - adjust the quantity of harissa to taste. Slowly add olive oil, blending after each addition, until the pesto has reached the consistency you want.
Slice the cherry tomatoe and deseed and dice the peppers. Fork the pesto through the couscous and mix in the vegetables.