Toast only the white sesame seeds before using. To toast, place the sesame seeds in a small, dry saute or frying pan over medium heat. Cook briefly, shaking the pan often and watching carefully to prevent burning. Remove the seeds from the pan as soon as they begin to turn brown. Set aside.
In a large saucepan, heat the olive oil over medium heat. Add the shallot, ginger, curry powder and turmeric and cook, stirring, until the spices are fragrant, about 1 minute.
Add the lentils, stock and coconut milk. Raise the heat to medium-high and bring to a boil. Reduce the heat to low, cover partially, and simmer until the lentils are tender but still firm, about 12 minutes. The mixture should be brothy; add a little water if needed.
Stir in the spinach, cover and simmer for about 3 minutes longer. The lentils should still hold their shape. Uncover and stir in the salt. Serve hot, garnished with the cilantro and toasted white or untoasted black sesame seeds.