Heat ghee in a large Dutch oven overmedium heat. Season chicken with salt andpepper. Working in batches, cook chicken,skin side down, until golden brown (donot turn), 8–10 minutes.
Transfer to a plate.
Add onion, garlic, and ginger to potand cook, stirring occasionally, untilonion is very soft and golden brown, 8–10minutes.
Add tomato paste, garam masala,cumin, turmeric, coriander, cayenne, andcardamom and cook, stirring often,until tomato paste is beginning to darken,about 4 minutes.
Add chicken, broth, tomato purée, and cream to pot; season with salt and pepper.Bring to a boil, reduce heat, and simmer,partially covered, skimming occasionally,until chicken is almost falling off the boneand liquid is slightly thickened, 1 1/2–2 hours.
Add potatoes to pot and cook, partiallycovered, until potatoes are fork-tender,chicken is falling off the bone, and liquidis thick enough to coat a spoon, 30–45minutes.
Remove skin and bones fromchicken, if desired, and return meat to pot;season stew with salt and pepper.
Divide stew among bowls, top withyogurt and mint, and serve with naan,flatbread, or rice.