Pop the broad beans out of their pods (see our tip below if you want to double pod them). Peel the shallots and cut them into quarters. Peel and thinly slice the garlic. Finely grate the zest from the lemon. Finely shred the sorrel leaves.
Crumble half the stock cube into a jug. Pour over 200ml hot water from the kettle. Swirl to dissolve it.
Heat a deep frying pan or wok for 1 min over a medium heat. Season the chicken thighs with salt and pepper. Add 2 tsp oil and the chicken thighs to the pan. Cook for about 15 mins till golden brown, turning 2-3 times.
Drain the pan of any excess fat. Add the shallots to the chicken.
Cook for 2 mins. Add the garlic. Cook for 1 min. Add the stock. Cover and simmer gently for 5 mins. If your pan doesn't have a lid, use a baking tray to cover it.
Add the buckwheat to the pan and shuffle everything about so the buckwheat is evenly distributed. Cover. Simmer for 10-15 mins till the buckwheat is tender and the chicken is cooked through. Stir the buckwheat now and then to make
sure it cooks evenly.
Turn the heat off under the chicken and leave to rest for a few mins. Cut the lettuce into 4 wedges. Melt the butter in a small frying pan till foaming. Add the lettuce and cook for 2 mins, turning once. Add the broad beans. Cook for 1 min more.
Stir the lemon zest into the broad beans and lettuce. Serve the chicken with the buttered lettuce garnished with the sorrel.