Heat the olive oil in a pan on a medium to low heat and throw in the shallots, celery and fennel. Stir well and let them sauté for a good 5 minutes until they begin to soften, then stir in the garlic and leeks and plenty of salt and pepper along with some fresh thyme and let them all gently sauté for another 5 min.
Add the broccoli, courgette and Brussels sprouts and let them sauté with the rest of the veg; then add the cavolo nero on top, place the lid on and let the whole thing sweat for another 5 min.
Pour in the stock, then add the peas, rocket and pearl barley, stir well and let it gently bubble away for 20 min. Finally, take it off the heat and let it cool for 5 minutes before serving.