Steam the herring roes until tender, but still firm.
Cut the roes into very small pieces. Season with salt and pepper.
Wipe out the frying pan with a piece of kitchen paper. Put in the butter and heat until the butter is bubbling.
Stir in the curry powder followed by the flour.
Cook, stirring, for 1-2 minutes, then add the vinegar and Worcestershire sauce. Combine all well.
Add the herring roes and simmer for 5-7 minutes. Adjust the seasoning to taste.
Meanwhile toast the bread under the grill.
Put a spoonful of stew on each piece of hot toast. Serve with chutney or tomato ketchup.