Scientists claim to have found the formula for the perfect chip butty – and say Brits are blundering by using too few chips.
Experts at Nottingham Trent University experimented with portion sizes, temperatures and timings in the study for supermarket Iceland.
They combined their results with the eating habits of 2,000 Brits surveyed to produce a recipe for the best butty.
According to their research, the key to a lip-smacking sandwich is achieving the optimum ratio of chips to bread – represented by the equation C * 3b/4 + k + 3m.
For the mathematically challenged, the formula for perfection is 12 freshly cooked, thick cut chips between two slices of buttered white bread with ketchup.
The most common mistake being made – by 37 per cent of Brits – is to use only seven or eight chips in a butty – 50 per cent too few, the scientists say.
Lead researcher Dr James Hind, a statistician from the university’s School of Science and Technology, says the ideal ratio of chips to buttered bread plus ketchup by weight is three quarters.
On that basis, a layer of 12 chips weighing around 60g should go between two 40g medium slices of white bread.
Any less than that ratio and Dr Hind warns that there may be insufficient chips to melt the butter required to soften the bread and create a tasty contrast to the crispiness of chips.
Too many chips and it will be awkward to eat the butty and every mouthful will taste of chips with the bread and butter going largely unnoticed, Dr Hind concluded.
Iceland’s survey found that the bread for a butty must be a sliced white loaf, preferred by over half – 52 per cent – of Brits.
Just 14 per cent favour a soft bread roll; nine per cent a bap; and eight per cent sliced brown bread.
It should be a medium sliced loaf (49 per cent) rather than thick sliced (26 per cent) or thin sliced (seven per cent).
The bread must be buttered (65 per cent) rather than relying on margarine (23 per cent) or any other spread and a thin layer of butter is best (64 per cent).
The chips should be thick cut (46 per cent) like those from the local chippy rather than standard oven chips (33 per cent) or skinny French fries (11 per cent).
Ketchup is the most popular condiment to add (49 per cent), followed by mayonnaise or vinegar (each 17 per cent).
Dr Hind’s equation for the optimum ratio of chips to bread is C * 3b/4 + k + 3m, where C is the weight of chips(g), b is the weight of the bread(g), k is the amount of ketchup (ml) and m is the mass of butter (g).
And it is not just Dr Hind who takes an academic approach with almost three quarters of Brits – 73 per cent – believing that making the perfect chip butty is an ‘exact science’.
The scientist’s step-by-step guide to creating the perfect butty is:
- Cook thick cut oven chips at 200C for 22 minutes
- Thinly butter two slices of medium sliced white bread
- While the chips are freshly cooked, place at least 12 on one slice of buttered bread so that their weight is three quarters that of the bread plus ketchup
- Squeeze as much ketchup as you like but add more chips to compensate so it doesn’t get too cold
- Place the second slice of bread on top of the still steaming hot chips
- Allow to cool for at least 30 seconds before enjoying. If it is too hot to hold, it is too hot to eat!
Dr Hind said: ‘What makes white bread preferable is that it is usually the softest. This makes it a perfect contrast to the crunchy chips. And sliced bread has a constant thickness, giving a more consistent chip butty.
‘The most important thing is to have the weight of chips at least three quarters of the weight of the bread plus ketchup.
‘But every type of bread and style of chip varies subtly, so I’d encourage people to experiment at home and devise their own perfect formula.
‘Personally, I much prefer brown sauce and you can substitute it for ketchup in the equation as you like.
‘One thing my formula ignores is salt. That’s a matter of personal taste – and personal health – and so that’s a great place for people to start their own experiments!’
Iceland’s chips cost from £1. An Iceland spokesperson said ‘The chip butty is one of the greatest culinary inventions in UK history.
‘We felt it our duty to ensure the British public know the optimum way to build their crispy potato sandwich.
‘Some may disagree with the formula, preferring a skinny fry or a bread roll, so we remind customers that although the science has spoken, we have a wide range of over 50 types of chips to satisfy anyone’s personal preference.’