The kitchen formulas you need to know to master pastry, cakes, pasta and more

My life is filled with kitchen maths these days, converting recipe amounts from metric to cups, measuring the volume of loaf tins and trying to standardise cake recipes. When you have an archive of thousands of recipes that have been developed over decades, measurements are not necessarily standard.

For a start, the sheer volume of kitchen equipment made for the home cook that you can buy easily has increased manyfold; the use of metric measures has been made standard (America, where are you on this?); and pack sizes used by supermarkets have changed. Goodbye 284ml pots of double cream, and hello 300ml. Digital scales have become affordable (did I mention I’m old?), sets of measuring spoons the norm, and the dessert spoon measure is on the way to retirement. Cooking is a science and art, so knowing your ratios gives you a solid foundation to work magic — God knows I’ve written recipes where I patently got the former wrong in testing. (Thank goodness for testing.)

Memorise these formulas and you’ll be set.

Pastry ratios

Drummed into me like a military roll call at catering college, the quantities for basic pastry are half fat to flour, meaning you weigh your flour and you’ll need half the amount of fat (butter, marge, or lard) to make a very easy-to-use pastry. Helpfully, before some packs of butter became 200g, you could buy a 500g bag of plain flour and a 250g block of butter, meaning you wouldn’t need to measure them (for a large batch of pastry, of which half can be frozen).

A splash of hydration may be needed to bring it all together — a tablespoon or two of water, milk or beaten egg, which also enriches the pastry. The more you up the fat in this equation, the ‘shorter’ the pastry will be, but the harder it is to work with, taking it all the way to shortbread, which – now we’re talking percentages – is two-thirds fat to flour. This is near-on impossible to roll out, but when pressed in place makes the finest pastry there is.

This equation also works for sweet and savoury pastry, with 250g plain flour and 125g butter being an ideal amount for a 23cm tart. From this, you have a blank canvas to tweak the pastry according to the dish you want to make. My favourites are:

• Sweet pastry – add 2 tbsp sifted icing sugar to the flour and use only a small pinch of salt.
• Almond pastry – use 200g plain flour, 50g almonds and 2 tbsp icing sugar.
• Brown sugar pastry – add 50g light brown sugar to the flour.
• Parmesan pastry – add 25g of finely grated parmesan to the flour.
• Rye pastry – add 50g rye flour and use only 200g plain flour.
• Spelt pastry – add 50g spelt flour and use only 200g plain flour.
• Wholemeal pastry – add 75g wholemeal flour and 175g plain flour; you might need a splash of cold water or milk to bring it together.
• Devilled pastry – add 1 tbsp mustard powder and a large pinch of cayenne.
• Thyme pastry – add 1 tbsp finely chopped thyme leaves to the flour.

Quiche equations

Armed with the perfect pastry, you now need something to fill it with — and as a nation, we love a quiche.

Though the ingredients you can put through a quiche are limitless, what holds those ingredients together is a savoury custard. For a 23cm quiche, that’s 3 eggs to 300ml double cream, or for a general savoury custard, 1 egg to 100ml double cream (1 to 1).

From this, you have a blank canvas to fill your quiche with whatever you want, though bear in mind that ingredients with a high water content, like cherry tomatoes, can dilute the custard as it cooks and stop it setting.

The crêpe code

Taught to me by our fabulous Head of Food, Cassie Best, and one that makes every Shrove Tuesday a cinch, is the 1–2–3 formula for perfect pancakes — or as I remember it, 3-2-1 dusty bin (sorry, that’s one for the Gen X-ers).

So, that’s 100g plain flour, 2 eggs and 300ml milk. For a lump-free batter that doesn’t require any sifting, whisk the eggs and flour together to make a paste, then gradually whisk in the milk until everything’s smooth.

The batter can be used straightaway, but it behaves a bit better and has a more pronounced flavour if left to stand for an hour or so. This will make about 10–12 small plate-sized, thin, lacy pancakes — as they should be.

Pasta by numbers

Though most dried pasta is a frugal mix of just flour and water, fresh pasta is usually enriched with egg, which gives it its richness and makes it a more premium commodity. The quantities to make your own dough are very easy to remember: 1 to 1, meaning 1 egg to every 100g ‘00’ flour.

The egg white hydrates the dough while the yolk enriches it — which is why some recipes use just yolks for a richer, deeper yellow dough. If an equation for that is needed, it would be 2 to 1, meaning 2 yolks to 100g ‘00’ flour.

Dressing logic

For a basic dressing, the ratio of acid to oil is 1 to 3 (1-2-3). If you’re making the dressing in a bottle or jar, the way to measure this without a jug is to cup your hand around the ingredients; the vinegar should come just past your little finger, and the oil should come up to the top of your following three fingers.

This ratio is for a basic dressing to which mustard can be added for punch and to temporarily emulsify. But not all vinegars have the same acidity, and depending on what you’re dressing, you might want a punchier dressing, in which case the ratios can be upped: 2 parts acid to 3 parts oil.

To the power of yeast

I’m yet to get a convincing answer on why bakers favour fresh yeast over dried, but they still do, and some older recipes are still written using fresh. Luckily, the equation for swapping to dried from fresh is half the weight given, and swapping from dried to fresh (though why you’d want to, I’m still waiting to be enlightened) is simply double the amount.

The equation for swapping dried yeast to wild (active sourdough starter) is × 10. Wild yeast doesn’t behave in exactly the same way — it’s a little slower — but it’s that tardiness that builds flavour and makes whatever you’re baking more digestible.

The sponge cake calculator

As MasterChef semi-finalist Henry Phillips cleverly points out in his social media video about making pasta, stating how many eggs are needed in something can vary depending on the size and weight of the eggs. Even when you state the size, they still differ in weight, so in some recipes it’s best to weigh the eggs first and build the rest of the recipe around that.

This is proven by a tip for the perfect sponge given to me by food writer Julie Friend. For the perfect sponge every time, weigh 4 eggs in their shells, and the rest of the ingredients (self-raising flour, butter and sugar) should all weigh the same. No need for that little splash of milk some recipes call for.

Once you’ve weighed your eggs, crack them into a bowl and add the same quantity of all the other ingredients, then whisk to a smooth batter and you’ll have the perfect sponge mix. Looking back at a sponge recipe I wrote years ago, this fits those rules — all the main ingredients are 200g plus 4 eggs which, when weighed, should come to (you’ve guessed it) 200g.

Yorkshire pudding solver

One of the first chefs I worked with at Good Food, a very long time ago, was the proud Yorkshireman Brian Turner MBE. He told me that the secret to yorkshires was equal volumes of flour, eggs and milk.

My foolproof yorkshire pudding recipe is based on this ratio. I measured the volume of a 12 yorkshire pudding tin and calculated the ingredients to fit. So whether that’s big ones, little ones or toads in the hole, ensure equal volumes for your batter and you’re set.

Liquid logic

Modern-day scales often have a liquid measure function. Unfortunately, different liquids have different densities, and this makes the scales inaccurate unless you’re just measuring water.

For other liquids (syrups, creams, honey etc), you’re better off measuring in a jug or using grams. Orlando Murrin has taken the time to note down what 100ml of various liquids weigh:

• 100ml milk weighs 103g
• 100ml double cream weighs 102g
• 100ml maple syrup weighs 135g
• 100ml honey weighs 142g
• 100ml sunflower oil weighs 92g
• 100ml brandy etc weighs 95g

Gelatine

As with fresh yeast, the default for using gelatine was always the harder-to-process leaf gelatine, which needs soaking, draining and dissolving in a warm liquid before being set. Powdered gelatine, on the other hand, just needs sprinkling into warm liquid and stirring to dissolve, like sugar in tea.

So if faced with a recipe that calls for standard leaf gelatine, the equation for changing it to powdered is ½ tsp per leaf — nice and simple.

If you have any food formulas or cooking equations of your own, let us know in the comments below.

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