Organize all ingredients in separate bowls. Dice your onion, carrots, and celery uniformly (about ¼-inch pieces). Cut apple into slightly larger pieces (½-inch). If using chicken, pat it dry with paper towels before cutting.
Heat olive oil in a large, heavy-bottomed pot over medium heat until it shimmers. Add onions and cook for 3 minutes until translucent. Add carrots and celery, cooking for another 4-5 minutes until they begin to soften.
Add minced garlic and grated ginger, stirring constantly for 30 seconds. Immediately add curry powder, cumin, coriander, turmeric, and cayenne (if using). Toast these spices for 60-90 seconds, stirring continuously to prevent burning.
Add chicken, stirring to coat with the spice mixture. Cook for 4-5 minutes until the exterior of the chicken pieces turns opaque. Add the diced apple and stir to incorporate.
Pour in the chicken broth, scraping the bottom of the pot to release any browned bits. Add chickpeas, red lentils, and the bay leaf. Bring to a boil, then reduce heat to maintain a gentle simmer. Cover partially and cook for 20-25 minutes, or until lentils are tender but not mushy.
Stir in coconut milk and simmer for an additional 5 minutes without boiling. Remove from heat and add lemon juice. Taste and adjust seasoning with salt and pepper. Remove the bay leaf before serving.
Serve in warmed bowls with a dollop of yogurt, fresh cilantro, and lemon wedges on the side.