Soften onion and garlic in oil and butter for a few minutes.
Add the Balti paste and the cubed potatoes. Cook on low for about 5 minutes, stirring to avoid sticking.
Now for the stock and cook, covered for about 5 more minutes, until potatoes are almost but not quite done.
Stir in the creme fraiche. Tip in the haddock and peas and simmer for about 5 minutes.
Taste. Squeeze lime, season and taste again. Serve with rice and fresh coriander.