Preheat an oven to 200°c/180°c (390°f/355°f).
Cut the sweet potatoes in half, score the flesh then drizzle over a tbsp of veg oil & season with salt & pepper. Place onto a baking tray & roast until soft, this will take around 30-45 minutes.
Whilst the potatoes are cooking, roughly chop the onion, carrot, garlic & ginger (don't worry about peeling the carrot!).
Next, place a large saucepan over a medium heat & add in 2 tbsp of veg oil. Once hot, add in the chopped up veg, bay leaf & thyme.
Season with salt & pepper then cook the veg until is has started to soften, 5-10 minutes. Make sure to stir the pan regularly to stop the veg from catching.
Next, pour in the coconut milk & chicken stock. Bring to a simmer then cook gently until all of the veg is nice & soft. This will take around 25 minutes, by which point the sweet potatoes should be cooked & cool enough to handle. Once the veg is cooked, spoon the potato flesh out of the skins & add into the soup (the skins can be discarded). Mash the sweet potato into the soup with a spatula then cook for a further 5 minutes. If the soup's looking a little thick, thin it out with some more stock. Remove the soup from the heat then stir in the miso.
Transfer the soup to a blender (you'll probably need to do this in batches) & blitz until smooth, adding more stock & seasoning if necessary.
Pour the soup into bowls & top with a drizzle of coconut milk, a sprinkling of sesame seeds & some freshly cracked black pepper.