Bring the chicken stock to a boil. Melt the butter on a gentle heat and add the onions, garlic, and chilli. Season with salt and freshly ground pepper and sweat for 3 to 4 minutes. Add the peas and cover with the hot stock. Bring to a boil and simmer for 5 to 8 minutes. Add the coriander and puree the liquid in a blender. Season with salt, freshly ground pepper and a pinch of sugar, which enhances the flavour even further. Serve with a swirl of softly whipped cream and a few fresh coriander leaves sprinkled over the top.