In a large bowl, cover the lentils and split peas with plenty of water, then let them soak at room temperature for at least 4 hours. You can also leave them to sit overnight. Drain the water, then rinse the lentils and split peas.
In a large stock pot, heat the olive oil over medium heat. Add the ground turkey, onion and garlic, and cook for about 5 minutes, breaking up the meat with a wooden spoon, until the meat is cooked through.
Add the salt, pepper and spices, and cook for 1 minute.
Add the chicken stock, diced carrots and potato, and the drained lentils and split peas.
Cover the pot, and bring to a boil over medium heat. Reduce to low and simmer, covered, for about 35-45 minutes, until the lentils and vegetables have softened.
Much of the liquid will be absorbed as the soup cooks, so add water, a half cup at a time, if you want a more brothy consistency. Taste the soup and add more salt, if desired.
For a thicker, creamier texture, remove 2 cups of the soup and blend it smooth in your blender. Stir the blended soup back into the pot. This step is completely optional.
For serving, I like a bit of crunch with the soup, so I topped mine with dry roasted edamame, pumpkin seeds, and homemade crusty bread.
The leftover soup continues to thicken as the lentils absorb more liquid, so add more water as needed.