Combine lentils, chicken stock and turmeric and simmer covered for 30 minutes.
Add potatoes. Simmer another 30 minutes. Keep an eye on the pot so it doesn't boil over.
Puree the soup in batches. Your blender works best. Return soup to pot.
Trim visible fat from the chicken. Cut into 1/3 inch chunks.
Add oil to a clean frying pan. Heat over medium heat.
Pay attention at this point. Add the garlic ginger paste and fry, stirring constantly until the splattering stops.
Add the spice mix and continue to stir constantly for another 30 seconds. Regulate your heat. Don't let the spices burn!
Add the chicken and continue to stir. Cook chicken until almost done - about 3 minutes.
Add chicken mixture to soup pot. Simmer 3 minutes. Add lemon juice. Simmer an additional 2 minutes.
Thin the soup with stock if needed. Adjust seasoning (salt) to taste. To my taste another teaspoon or a bit more works. But everyone is different. Creep up on it. Can always add more. Cannot take it away.
Serve with a spoonful of raita or drizzle with a bit of heavy cream.