1. Peel and finely slice the red onion. Halve the red peppers, scoop out the seeds and white pith, then slice the peppers into 1cm-thick strips. Trim the courgette, halve it and slice it into 1cm-thick slices. Scrub the potatoes and slice them into 1cm thick slices. Set the veg to one side.
2. Place the chicken breasts between two sheets of baking paper and bash with a rolling pin, pestle or meat mallet till they are around 2cm-thick all over. Season them with salt and pepper and rub them with ½ tbsp olive oil each.
3. Warm a large, deep frying pan or shallow casserole dish over a medium heat for 2 mins, then add the chicken breasts to the pan. Fry for 3 mins till the chicken is golden underneath, then flip the chicken over and fry for another 3 mins till it’s browned all over.
4. Lift the chicken out of the pan and set aside on a plate. Add the red onion, peppers, courgette and potatoes to the pan with ½ tbsp oil. Season with a pinch of salt and pepper. Turn the heat down a little and fry for 10 mins, stirring every so often, till the veg pick up a little colour.
5. While the veg fry, crumble the stock cube into a heatproof jug and stir in 350ml boiling water. Peel and grate or crush the garlic. Finely grate the zest from the lemon.
6. Stir the garlic and lemon zest into veg with 1 tsp dried oregano. Nestle the chicken breasts back into the pan and pour in the chicken stock. Pop a lid on the pan (or cover it with a baking tray if you don’t have a lid). Turn the heat up a little, bring to the boil and then turn the heat down a little and simmer for 15 mins till the veg are tender and the chicken breasts are cooked all the way through.
7. While the chicken and veg cook, pick the leaves off the parsley stalks. Pick the thyme leaves off their stalks (if the thyme is woody, you can push them through a sieve and the leaves will collect in the sieve. If the sprigs are white and very soft, then you can just roughly chop the leaves and sprigs together as they’ll be tender enough to eat). Roughly chop the herbs together.
8. When the chicken is ready, stir half the herbs into the pan and squeeze in the juice from half the lemon. Divide the chicken and veg between 2 warm plates and garnish with the remaining herbs to serve.