method
1. Peel and thinly slice the onions and potatoes. Melt half the butter in a skillet, add the onions and cook till transparent.
2. Add remaining butter and potato slices and fry for 15 minutes, turning occasionally.
3. Meanwhile, wipe the haddock and pat dry with kitchen paper. Cut into small pieces and coat with seasoned flour. Add to pan and cook for a further 15 minutes, stirring from time to time.
4. Season with salt and pepper. Add parsley and vinegar and cook over a high heat till vinegar evaporates. Serve immediately with grilled tomatoes.
