Allow the mint ice-cream to soften until easily spreadable. Meanwhile line the tin with a double layer of cling film, allowing a 10cm excess to hang over the edges.
Once soft, spoon the ice cream into the tin, compact it down and spread it out evenly with the back of a spoon. Cover with the excess cling film and freeze for 1 -2 hours until frozen solid. This can be prepared up to a few months in advance.
When ready to assemble, lay two ice-cream sandwiches beside each other at one end of the serving plate, with the rectangles pointing in the same direction as the plate.
Unwrap the frozen mint ice-cream block and sit it on top.
Arrange the remaining four ice-cream sandwiches on top of that. Cover and return to the freezer.
Whisk the egg whites in a food mixer until soft peaks form. Gradually add the sugar in stages, continuing to whisk.
Add the vinegar and peppermint extract and continue to whisk until really stiff and glossy.
Spoon into the piping bag, which you may have to refill once or twice.
Pipe meringue peaks in neat rows all over the sides and top of the ice-cream loaf. Alternatively, simply spread it on with a palette knife, creating whatever pattern you like.
Use a blowtorch to brown the meringue all over or toast briefly under a hot grill. Serve at once, decorated with pretty bunting if you like. Cut into 10 even-sized slices. This is best done with a long sharp knife, dipped in boiling water and wiped dry between each cut.