How to make the perfect Yorkshire puddings, according to scientists (who claim they should be 10cm long!)

Whether you eat beef, lamb or even chicken, no Sunday roast is complete without a Yorkshire pudding.

Recently voted Britain's most prized regional delicacy, this mouth-watering cup of cooked batter can be the trickiest item on the plate to get right.

Even chefs from top restaurants and expensive gastro pubs have been known to mess up.

And is there anything worse than a Yorkshire Pudding that is too flat, too dry or simply stone cold?

To mark National Yorkshire Pudding Day today, MailOnline has provided a step-by-step guide to making the perfect Yorkie, according to science.

According to scientists from the Royal Society of Chemistry (RSC), a recipe for Yorkshire pudding consists of just five ingredients: plain flour, milk, water, eggs and salt.

The RSC recipe calls for strictly plain flour – not self-raising flour, with baking powder added.

Baking powder or baking soda should not be added to the mixture at all, as this can result in flatter, deflated puddings that have not risen properly.

'One theory is that they will let the batter rise too quickly before the gluten has time to strengthen the mix and then it will collapse,' British food technologist and Yorkie fan Elizabeth Head told MailOnline.

In addition, bicarb can make the batter too 'cakey' or increase the risk of burning, according to RSC.

For the liquid, RSC claims chefs should use 92 percent milk and 8 percent water, rather than just milk as is commonly done in the country's kitchens.

The extra moisture from the water leads to lighter, puffy Yorkies, because the movement of the steam created by the heat encourages them to puff upward.

No less important are the eggs, which also add moisture and act as an emulsifier, binding the ingredients together.

Two eggs are sufficient for a batch of six puddings, together with 250ml liquid (230ml milk and 20ml water), 85g flour and half a teaspoon of salt.

Once the batter has been whipped into a thin consistency similar to whipped cream, it should be stored at room temperature and not refrigerated.

Mrs Head told MailOnline: 'Batter should be at room temperature so it rises better when it hits the hot oil.

'When the batter hits the hot oil, the oil can heat a room temperature batter more easily than a very cold batter.

'A cold mixture rises less well and you get a thick pudding.'

If you follow these steps correctly, this should yield Yorkshire puddings that are at least 4 inches high; shorter than that and they are not technically Yorkshire puddings, RSC claims.

One of the most important tips is not to open the oven door while the Yorkies are cooking, as Ms Head says they can deflate from the cooler room temperature air.

Of course, the perfect Yorkshire pudding recipe varies from chef to chef.

Heston Blumenthal, known for his scientific approach to cooking and gastronomy, published a recipe for the perfect Yorkshire pudding in his latest book 'Is This A Cookbook?'

He says 'good hot oil' is the key to a great Yorkshire pudding, and he chooses vegetable oil because it has a high smoke point (RSC suggests using beef drippings for the same reason, while Mrs Head opts for lard).

The incredibly hot fat not only cooks the batter quickly, but also creates a protective layer that helps prevent the batter from sticking to the pan, says Blumenthal.

Only 5mm of oil should be placed in each hole of a Yorkshire pudding mold before preheating to 230°C/446°F.

Once the oil is 'smoking hot', the batter should be poured in – a layer about one cm deep per hole – and the baking tray placed on the middle shelf of the oven.

'Avoid shaking the baking tray and mixing the oil and batter, which can result in greasy Yorkshire puddings,' says Blumenthal.

Although the top of the oven is the hottest spot, the middle shelf is the best place for the puddings as they are likely to have more room to rise, he adds.

About 15 minutes in the oven should be enough, or until they are nicely browned and fully puffed.

As a cheeky optional extra, chefs can add a spoonful of English mustard to the batter for a bigger-flavored pud, Blumenthal suggests.

Like many of Britain's best-loved dishes, the exact origins of the Yorkie are unclear, although the consensus is that it has always been associated with the north of England.

According to Hazel Flight, a nutritionist at Edge Hill University in Lancashire, the dish was originally known simply as 'batter' or 'dripping pudding'.

The prefix 'Yorkshire' was first added in 1747, in the best-selling cookbook 'The Art of Cookery Made Plain and Simple' by cookery writer Hannah Glasse, a Londoner.

Back then it was always served as a separate dish before the main meal, usually with gravy made from the juices of the roast.

Yorkshire housewives served Yorkshire puddings before meals so they ate less of the more expensive main course.

As for why it was even called 'pudding' in the first place, originally puddings were not always intended to be sweet as we know them today.

The word 'pudding' comes from the French word 'boudin', which in turn comes from the Latin 'botellus' – both words for small sausages.

In medieval England, the use of the word 'pudding' probably referred to the sausage as it was wrapped in the batter.

But in the years that followed, the name “pudding” persisted even when there was no meat.