Warm a frying pan over a medium heat for 2 mins. Add ½ tbsp oil and the chicken breast. Fry for 8-10 mins, turning every so often, till the chicken is browned and cooked through – if you slice a thick piece open, there won’t be any pink flesh.
Meanwhile, make the salsa. Finely chop the tomatoes and pop them in a bowl. Peel and finely chop the shallot and add to the tomatoes. Grate in the lemon zest and squeeze in the juice from half the lemon. Halve the chilli, flick out the seeds and white pith and finely chop it. Add to the bowl. Finely chop the coriander stalks and stir them into the salsa with a pinch of salt and pepper.
The chicken should be cooked by now. Take it out of the pan and set it on a plate to cool slightly.
Wipe the pan clean with kitchen paper. Add 1 tsp coriander seeds to the frying pan and toast for 2 mins. Tip into a pestle and mortar and roughly crush. No pestle and mortar? Use a small bowl and the bottom of a jam jar.
Stir the crushed coriander into the salsa with 1 tsp ground cumin. Taste and adjust the seasoning if you think it needs it.
Roughly chop the chicken. Coarsely grate the cheddar. Lay a tortilla on your work surface. Place 1 tbsp chicken, 1 tbsp salsa and a large pinch of cheddar in the middle of the tortilla. Fold 2 sides over the filling to make a rectangle. Bring the short edges up and press them down to make a parcel. Set on the work surface, folded-side down, to hold the parcel together. Repeat with the remaining tortillas. Set any leftover filling to one side.
Put the frying pan back over a medium heat. Add ½ tbsp oil to the pan and 2 of the chimichangas, placing them folded side down (make sure to tuck the sides in if they start to spring open). Fry for 2-3 mins till golden and crisp, then carefully turn over and fry for another 2-3 mins. Lift out of the pan and pop on a warm plate. Add another ½ tbsp oil to the pan and the remaining 2 chimichangas. Fry for 2-3 mins on each side till golden.
While the chimichangas cook, toss the salad mix with ½ tbsp olive oil, a squeeze of lemon juice and some salt and pepper.
Serve the chimichangas with the salad and any remaining chicken, salsa or cheddar on the side.