Light, lean and chunky Thai soup with a little heat for good measure.
Heat a Dutch oven over medium heat. Add oil to pan and swirl it around to coat the surface. Add mushrooms and the next 4 ingredients (through lemongrass) and cook the whole thing for 3 minutes, stirring occasionally.
Add chile paste to the pan and cook for 1 minute. Add in Chicken Stock, coconut milk, fish sauce, and sugar, then bring it to a simmer. Reduce the heat to low and let it simmer for 10 minutes.
Finally, add the chicken to the pan. Continue cooking for 1 minute or until it's thoroughly heated. Ditch the lemongrass, then top with onions, cilantro, and juice.