Attention all cooks. Scientists have produced the answer to the eternal question: how tall is the perfect Yorkshire pudding?

The Royal Society of Chemistry has decreed that a Yorkshire pudding must be no less than four inches (10cm) if it is to be worthy of the name; any less, and the dish cannot be properly said to have risen.

Dr John Emsley, a chemist who himself hails from Yorkshire, was asked to draw up the definitive recipe and dimensions after the society was contacted by an expatriate cook struggling to produce the delicacy in his Colorado kitchen. Dr Emsley’s consultations with colleagues across the country led the Royal Society of Chemistry to conclude that the best specimens were no less than 4in high. He declined to disclose the precise methodology of the investigation.

“I have seen many grim results from people who have tried to get their Yorkshires to rise,” he said. “They frequently made gross errors.

“Cooking is chemistry in the kitchen and one has to have the correct formula, equipment and procedures. To translate the ingredients into chemical terms, these are carbohydrate + H2O + protein + NaCl + lipids.”

Northerners do have a natural gift for creating the Yorkshire pudding, he said. “It’s in the blood and instinct of people born and raised there. You can tell from the look and taste if the cook has the right touch, and it is almost pitiful to observe the stuff that comes from some southern ovens — flat, pale and soggy much of the time. Some amateurs even place the batter in the fridge first. What kind of foolish act is that?”

The crucial research project had begun when Ian Lyness, an Englishman living in Boulder, e-mailed the Royal Society of Chemistry seeking a scientific explanation for his Yorkshires emerging flat when he cooked them in Colorado — yet rising when he made them at lower altitude in other states. Mr Lyness said: “I use batter mix that I pick up on my trips back to Blighty and my mum’s old Pyrex dish. Perhaps the secret is to make them as she, as a true Yorkshirewoman, did. I try to follow in her steps. I do not go for the silly little ones on the plate with everything else, but a traditional, big long pudding which she always served as a separate first course with gravy before the roast beef, lamb or whatever.

“Colman’s English Mustard is also an essential accompaniment, I find.

“But I have been struggling here. On Sundays from my kitchen window I can enjoy the sight of snow-capped mountains but on my plate there are apologetic little hillocks.”

It was while investigating the impact of mountain air upon the rise and fall of the Yorkshire pudding that scientists agreed that 4in was the height to aim for.

The society has many members working in the fields of food and nutrition, including the award-winning chef Heston Blumenthal. Next year it will produce a leaflet on how to make the ideal 4in Yorkshire pudding and argue for its renaissance as a dessert.

Not everyone welcomed the scientists’ dictum. Rose Gray, co-founder of the River Café, told The Times: “Four inches is far too high, in my book. That would leave them dry on top and soggy in the middle. When they are thin and flat, after being cooked in the meat juice, the flavours taste much more interesting.”

Gill Holcombe, author of a new budget cookbook, writes that it is vital to use plain flour. “If you use self-raising you’ll get a flat, solid result — and make sure the oil is at least fizzing, if not smoking hot, when you pour the batter in.”

Royal Society recipe

Ingredients

Tablespoon and a half of plain flour

1 egg

Half milk, half water for thin batter

Half a teaspoon of salt

Method

Put flour in a bowl, make a well in the middle, add the egg, stir until combined then gradually add the milk and water until the batter is a smooth and thin consistency

Stir in half teaspoon of salt and leave to stand for 10 minutes at room temperature

Put beef dripping into Yorkshire pudding tins but don’t use too much fat. Put into hot oven until the fat starts to smoke

Give the batter a final stir and pour into the tins. Place in hot oven until well risen – 10 to 15 minutes

Serve

Always serve as a separate course before the main meal and use the best gravy from the roast joint. (Yorkshire housewives served it before the meal so they would eat less of the expensive main course)

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