Heat oil in a large pan over a medium-high heat. Add onion and garlic, and sauté for 2-3 minutes.
Next add the curry paste and cook until fragrant. Add some water if needed to stop it sticking.
Pour in the coconut milk and stock. Bring to the boil and cover. Lower the heat and simmer for 5 minutes.
Add the vegetables and fish. Leave to poach for 4-5 minutes or until the fish is cooked through and opaque.
Once the fish is cooked, season the curry with the fish sauce, brown sugar and lime juice; adding more of each if needed to balance the flavour to your tastes
Serve on rice and garnish with coriander.
Notes
You can use any seasonal vegetables you have available or frozen/canned vegetables such as green beans, baby corn etc