Pop the chicken in a bowl. Add the Thai red curry paste. Stir to coat the chicken in the paste. Put to one side.
Peel and grate or crush the garlic. Finely slice the chilli. Flick out the seeds and white bits for less heat. Trim the tough outer layer off the lemon grass. Bash it a few times with the flat side of your knife to lightly bruise it.
Finely slice the mushrooms. Halve the cherry tomatoes. Snap the woody ends off the asparagus. Chop the spears into 3 cm long chunks. Fill the kettle and boil it.
Warm 1 tbsp olive oil in a pan. Add the chicken. Fry over a medium heat for 5 mins till the chicken is browned all over. Stir every so often so it cooks evenly.
Add the garlic, chilli, lemon grass and lime leaves. Cook and stir for 1 min till the pan smells aromatic. Add a pinch of salt.
Add the mushrooms and asparagus to the pan. Pour in 850ml hot water from the kettle. Pop on the lid. Bring to the boil. Turn the heat down. Simmer for 5 mins, to just cook the vegetables.
Add the cherry tomatoes to the pan. Simmer for another 2 mins till the chicken is cooked through and the veg are tender.
Fish the lime leaves and lemon grass out of the soup. Taste it and more salt if you think it needs it. Serve straight away.