Start by preparing your ingredients: dice the chicken thighs, peel and chop the onion, carrots, and apple, and mince the garlic and grate the ginger.
In a dry skillet over medium heat, toast the curry powder, turmeric, and cumin for about 30 seconds until fragrant—this enhances their aroma and flavor.
Add a splash of oil to the skillet if needed, then stir in the diced onion, carrots, garlic, and grated ginger. Cook until the onion becomes translucent and fragrant, about 5 minutes, stirring occasionally.
Transfer the sautéed mixture to your slow cooker, then add the chicken pieces, rinsed lentils, chopped apple, coconut milk, chicken broth, and a pinch of salt and pepper.
Set your slow cooker to low and cook for 6 to 8 hours. As it cooks, the mixture will bubble gently and fill your kitchen with warm, spiced aromas.
About 15 minutes before serving, check that the lentils are soft and the chicken is tender—use a fork or probe. The soup should be thickened and fragrant.
Taste the soup and adjust the seasoning with more salt, pepper, or a squeeze of lemon if desired, to brighten the flavors.
Turn off the slow cooker and let the Mulligatawny rest for a few minutes. Then, ladle it into bowls, garnishing with fresh herbs if you like.
Serve hot with crusty bread or rice on the side for a complete, comforting meal. The soup should be creamy, fragrant, and filled with tender chicken, lentils, and a hint of apple sweetness.
