Add the peanuts to a dry wok or deep frying pan. Toast over a medium heat for 4-5 mins till they’re golden brown. Tip them onto a clean tea towel. Gently rub them to rub off most of the skins. Finely chop the peanuts and tip into a bowl.
Prepare the veg: peel the sweet potatoes and slice them into wedges about as thick as your thumb. Halve the pepper. Scoop out the seeds and white bits. Roughly chop the pepper. Peel and grate the ginger.
Warm ½ tbsp oil in the wok or deep frying pan. Add the sweet potatoes. Toss to coat in the hot oil. Fry for 8-10 mins, turning now and then, till the potatoes are a little golden brown.
Add the red pepper and ginger to the pan with the Thai red curry paste. Stir in most of the peanuts (keep a pinch for garnishing). Pour in the coconut milk. Add 300 ml boiling water. Add 1 tbsp tamari.
Cover and simmer for 12-15 mins till the potatoes are tender. Taste the stew and add more tamari if you think it needs it.
Gently stir in the spinach. Simmer for 2-3 mins, uncovered, till the spinach is wilted.
Ladle the stew into warm bowls and serve straight away, garnished with the remaining chopped peanuts.