Tip the red lentils into a bowl. Cover with cold water. Set aside to soak.
Peel the squash. Halve it and scoop out the seeds (see our tip on what to do with them). Roughly chop the squash into bite-size chunks.
Peel and finely slice the shallot. Peel and grate or crush the garlic. Finely chop the coriander stalks (keep the leaves for later).
Roughly chop the chicken into bite-sized pieces. Warm a large pan over a medium heat for 1 min. Add ½ tbsp oil and the chicken. Fry for 8 mins, turning once or twice, till golden.
Add the squash and shallot to the pan. Drain the lentils and add them too. Add 2 tsp mild curry powder, the garlic and coriander stalks and stir them in. Add a pinch of salt.
Pour in the chopped tomatoes. Top the pan up with 300ml boiling water. Cover and bring to the boil, then turn the heat down and simmer for 20 mins till the squash and lentils are tender. Stir occasionally and add a splash more water if it starts to stick.
Taste and add a pinch more salt and some pepper if you think it needs it. Ladle the curry into warm bowls. Top with the coriander leaves and serve.