Heat the sesame oil in a large pot with a lid
Add the red onion and cook over a low heat for 5 minutes
Add the garlic, ginger, chilli and spices and cook for a minute or two until aromatic
Add the sweet potato and stir to coat well.
Add the lentils and stock and some salt and pepper to taste. I don't usually add salt as the stock can be quite salty.
Bring the pot to a boil, then reduce the heat and simmer gently for 20 minutes, stirring occasionally until the lentils and sweet potato are cooked. You may need to add a little extra water to prevent it catching.
Stir in the spinach. Once the spinach has wilted serve immediately topped with the basil