Wash potatoes, leave the skin on. Chop potatoes into small cubes and add to a saucepan filled with water. Bring to a boil and leave to cook while preparing the curry mix.
Heat the oil in a large pot on medium-high heat, then add the chopped onions, cooking until the onion is translucent. Once translucent, add the garlic and stir constantly for 2 min.
Add the tinned tomatoes and lentils, then stir in the turmeric, paprika, curry powder and vegetable broth. Bring to a boil, then lower the heat and simmer for 15min.
Turn the heat down to low, then stir in chilli flakes, also adding the spinach on top of the curry. Cover the pot and leave the spinach to steam and wilt, befor stirring it into the mixture and distributing evenly.