Parboil your prepared potato chunks in a pan of boiling water for 5-8 minutes. Drain in a colander and leave to steam for a minute or two to dry.
Shake your potatoes in the colander to roughen up their edges.
Pour 1 tbsp of the vegetable oil into a baking tray and put it into the hot oven for 5 minutes until hot.
Add your potatoes to the hot oil, shake to coat and sprinkle with a little salt.
Roast in the hot oven for 30-45 mins, turning once, until brown and crisp.
(Optional) Drain on a wire rack over a tea towel to remove excess oil and allow them to crisp up even more.
Fry the onion very gently in the remaining vegetable oil with the lid on for about 10 - 15 minutes until soft and beginning to brown.
Add the garlic and ginger and sizzle it all for a further minute.
Add the dry spices and fry for 10 seconds until aromatic.
Add the water, stock cube, a pinch of salt and a good grinding of black pepper. Simmer it all together gently for about 10 minutes until reduced to a thick, glossy sauce.
Stir in the prepared potatoes, heat through gently until piping hot and serve.
Notes
Nutritional information is only an approximate guideline. Calculations will vary according to the ingredients you use and your cooking methods.