Preheat the oven to 200°C.
Blend all marinade ingredients into a smooth paste.
Make deep diagonal slashes into the chicken breasts, thighs, and drumsticks down to the bone.
Place the chicken breast-side up on a foil-lined roasting tray.
Rub the marinade paste thoroughly into the chicken cuts and rest for 30 minutes.
Sprinkle chilli powder and black pepper over the bird and wrap tightly in foil.
Bake the chicken in the middle of the oven for 1 hour.
Unwrap the foil and cook uncovered for 15 minutes while basting periodically.
Verify chicken is cooked by checking that thigh juices run clear.
Preheat the oven to 180°C.
Coat potato chunks with oil, salt, and pepper in a bowl.
Spread potatoes on a baking tray and roast for 20 minutes.
Mix coriander, cumin, turmeric, and Kashmiri chilli powder on a plate.
Roll the partially roasted potatoes in the spice mix until fully coated.
Roast potatoes for another 20 minutes until tender and browned.
Rest the chicken for 15 minutes before carving and serving with the potatoes.