Quarter the tomatoes and place them in a large baking dish or roasting tray (roughly 25cm x 30cm). Peel the onions and cut into large wedges, then deseed and roughly chop the peppers. Add all these to the tray along with the chicken thighs.
Squash the unpeeled garlic cloves with the back of your knife and add to the tray, then sprinkle over the vadouvan.
Add 2 tablespoons of oil, the balsamic and a good pinch of sea salt and black pepper. Toss everything together really well to coat, then spread across the tray, making sure the chicken isn’t covered by the vegetables.
Roast for around 1 hour, or until the chicken is golden and cooked through, turning and basting it a couple of times during cooking with the juices from the tray.
Serve the traybake with a lovely green salad on the side. You could also buddy it up with a little rice, polenta or a loaf of crusty bread to mop up the juices.