Combine yoghurt, tomato paste and curry paste in a medium bowl and stir to combine. Add chicken and mix to coat in the mixture.
Heat oil in a large pan over a medium heat, add onion and cook for 10 minutes or until softened. Add ginger and garlic and cook for a further 2 minutes.
Add chicken and the paste mixture to the pan, making sure you scrape all the paste in. Cook the chicken for five minutes, or until it starts to colour.
Add capsicum, tinned tomatoes, lentils (liquid and all), coconut milk. bring to the boil, reduce the heat and simmer for 1 hour, stirring occasionally. Add additional water if it becomes too thick.
Break the chicken apart with the back of a spoon, it should come apart easily. Stir in the spinach (I did this in three batches).
Serve with rice, extra veg (I usually use beans, broccoli or frozen peas) and add a dollop of greek yoghurt and 1 tsp of mango chutney on top.
Enjoy!