Place the chicken, chopped lemongrass, garlic, ginger, fish sauce and half the curry powder or paste in a bowl and toss to combine, then cover and refrigerate for 1 hour (or up to overnight).
Preheat your oven to around 130oC or set a slow cooked to low.
Transfer the mixture to a slow cooker or casserole dish if using the oven.
Mix the rest of the curry powder or paste with a little of the stock and add to the dish along with the vegetables, the rest of the stock, coconut milk, stevia, lemongrass ends and bay leaves.
Stir to combine and cook on low for 7-8 hours or high for 3-4 hours.
If you like a thicker curry, 20 minutes before serving, remove 4 tbsp of the liquid and whisk in the arrowroot, cornflour or chia bran then pour back into the curry and stir through.
Replace the lid and cook at a higher temperature for the remaining 20 minutes.