Heat the coconut oil in a large saucepan over medium-high heat. Add the curry paste and stir until well incorporated, cooking for about one minute.
Add the lemongrass and ginger, cooking for an additional minute.
Add the chicken thighs, browning on each side for 2 minutes, then add in your coconut milk, lime juice, and zest. Cover and gently simmer for 30 minutes until the chicken is tender.
Remove the lid and cook for another 10 minutes. Add the chopped mango and spinach and cook for another 5 minutes.
Scoop into bowls, adding fresh herbs and serving over hot rice.
Make ahead tip: You can make both the curry and grains in advance, simply keep them separate and reheat when ready to serve. Lasts well in the fridge for up to 5 days and in the freezer for two months.