In a wok, add oil/butter, once heated, add all the spices (you can skip this part if u only have the powdered spices) except curry, black pepper & chilli flakes.

Add the carrots, onions, tomatoes, mashed potatoes, stir then add water, yoghurt and the curry, pepper, chilli flakes.

Stir until combined, cover & cook until it thickens.
You can add the stock left from the pepper soup