To make the curry paste, place a large non-stick frying pan over a high heat (no need to spray with low calorie cooking spray). As soon as the frying pan is hot, add the onion, garlic and ginger, stir and toast for about 4–5 minutes until a little charred around the edges. This will add a hint of smokiness to the finished curry. Transfer to a food processor and set aside.
Reduce the heat to medium and add the chilli flakes, cumin, cardamom, coriander, cinnamon and cloves. Stir well and toast for about 30 seconds until you can smell fragrant flavours being released, taking care not to burn the spices.
Add the toasted spices to the food processor containing the charred ingredients. Add the lemongrass and water, and blitz to form a coarse paste. Set aside.
Spray the frying pan with low calorie cooking spray (no need to wash the frying pan first), and place on a medium heat. When the frying pan is hot, add the pork and seal on all sides, stirring, for about 3–4 minutes. Add the curry paste and continue to cook for a further 2–3 minutes, stirring well.
Transfer the pork and curry paste to the slow cooker. Add the potatoes, coconut milk alternative, beef stock, fish sauce, tamarind paste, sweetener or sugar and peanut butter. Stir well to combine all the ingredients then cover with the lid.
Cook on the high setting for 4–5 hours, stirring halfway through if possible. When the curry is ready, the chunks of potato will be soft, some will have broken down to thicken the curry sauce and the pork will be tender. If the sauce is too thick for your taste, add a little water to thin it down. If it is too thin for your taste, cook uncovered for a short time to reduce further.
Just before serving, stir in the torn basil leaves. Sprinkle red chilli slices and a few fresh basil leaves on top. Serve with Basmati rice or other accompaniment of your choice.