Preheat the oven to 200°C. Cut the potatoes into chips about 1cm (1/2 in) wide and place in a bowl of cold water to rinse off the starch. Drain the chips in a colander, then dry them using kitchen paper. Place them on a large baking tray, spray with low-calorie cooking spray and sprinkle over the garam masala, garlic granules. Season with salt and black pepper. Turn the chips to coat all over.
Place the chips in the preheated oven for 20 minutes, turning the chips once. The chips will be slightly tender at this point but not completely cooked. Remove from the oven and set aside. Lower the oven temperature to 160°C.
Spray a large saucepan with low-calorie cooking spray and place over a medium heat. Add the onion, garlic and mushrooms and cook for 4-5 minutes, until starting to soften.
Add the mushy peas, chopped tomatoes, baked beans, curry powder, chilli powder, sweetener or honey and crumble in the stock cubes. Bring to the boil, then lower the heat and simmer, uncovered, for 20 minutes, stirring occasionally.
While the sauce is cooking, spray a large frying pan with low-calorie cooking spray and place over a medium heat. Add the chicken broccoli, cauliflower and green beans, and cook for 4-5 minutes, to seal the chicken on all sides.
After 20 minutes, remove the curry sauce from the heat and blend in a food processor or using a stick blender. When smooth, add to the chicken and vegetables in the frying pan and simmer, uncovered, for a further 10 minutes. Taste and season with salt and black pepper, if needed.
Transfer the chicken curry filling to a medium ovenproof dish and spread out evenly. Place the chips on top of the filling in an even layer. Place on a baking tray and then place in the oven at 160°C for 15-20 minutes, until the pie filling is piping hot throughout and the chips are golden and soft inside.
Serve with steamed vegetables or with Simple Naan Bread to mop up the curry sauce, or with other accompaniments of choice.