Place the chicken breasts between two sheets of cling film and bash with a rolling pin to flatten them out a little, so they are evenly thick. Warm a casserole dish or deep frying pan for 2 mins. Add 1 tbsp oil and the chicken breasts. Fry for 4-5 mins to brown, then flip and fry for another 4-5 mins to brown the other side.
While the chicken fries, trim the ends off the leek. Slice a cross 3cm deep into the top of the leek. Open it out and rinse out any grit. Finely slice the leek. Roughly chop the tomatoes. Peel and grate the garlic and ginger. Finely grate the zest from the lemon.
Lift the chicken out of the pan and pop on a plate. Add the leek to the pan with a splash of water and a pinch of salt and pepper. Turn the heat down to medium and cook, stirring once or twice, for 5 mins till the leek is soft.
While the leek cooks, drain and rinse the chickpeas. Crumble the stock cube into a heatproof jug. Stir in 300ml boiling water.
Stir the tomatoes, garlic, ginger and lemon zest into the leeks. Tip in the chickpeas. Add 2 tsp of the ras el hanut and stir well to mix.
Slide the chicken breasts back into the pan with any juices from the plate. Pour in the chicken stock. Cover, turn up the heat and bring to the boil. Once it's boiling, turn the heat down and simmer for 15 mins till the chicken is cooked through.
While the tagine simmers, tip the bulgar wheat into a heatproof bowl. Pour in 250ml boiling water. Cover with cling film or a plate and leave to soak.
Squeeze the lemon juice into the tagine. Taste it and add more salt or pepper if you think it needs it. Drain the bulgar wheat, if it needs it, and divide between two warm plates or bowls. Top with the chicken and chickpea tagine.