Place all ingredients, apart from spinach, curry leaves 2 tbsp olive oil and nigella seeds, into a slow cooker on high and stir to coat the potatoes well.
Stir potatoes once every hour or so and cook for three hours on high (or 5 hours on low) or until the potatoes are cooked through.
Meanwhile heat the remaining 2 tbsp of olive oil in a small pan over medium heat. Cook the curry leaves for around 30 seconds or until green, glossy and crisp and set aside on paper towel to drain.
When the potatoes are ready, stir through the spinach to wilt then serve sprinkled with nigella seed and crisp curry leaves.
TIP: The curry leaves are optional but will take your potatoes to the next level.