Sauce and dressing secrets: the 3:1 ratio, pasta water, and how to rescue a split sauce

Almost every sauce rests on two things: an emulsion (oil and water bound into one) and a balance of flavours — salt, acid, sweetness and depth (umami). If a sauce tastes flat, it's usually missing acid, not salt.

Let's go in order: dressings, mayo, pan sauces, cream sauces and thickening.

The classic vinaigrette ratio is 3 parts oil to 1 part acid (vinegar or lemon juice). If you like it sharper, go 2:1.

To stop the dressing separating within a minute, you need an emulsifier. The best one is mustard: it contains compounds that wrap around oil droplets and keep them from merging. Honey helps too and softens the acid.

An important detail: salt doesn't dissolve in oil. So first dissolve the salt in the vinegar or juice, then add mustard, and only then pour in the oil in a thin stream while whisking with a fork — or just shake it all in a closed jar.

Mayonnaise splits for two reasons: ingredients at different temperatures, and adding oil too fast at the start. Everything should be at room temperature.

The most reliable method is a stick blender in a tall, narrow jar. Put in a whole egg, mustard, salt and lemon juice, then pour all the oil on top. Push the blender to the very bottom, switch it on and hold it still for 10–15 seconds — a white emulsion will start forming at the bottom. Then slowly lift the blender, drawing in the rest of the oil. In a minute the mayo is done.

Use neutral sunflower or canola oil. Extra-virgin olive oil can turn bitter when blitzed.

The water you cooked pasta in is full of starch. That starch binds oil and cheese to the liquid, so the sauce doesn't separate — it turns silky and coats the pasta.

Before draining, scoop out a mug of the water. Combine the pasta with the sauce in the pan, add 50–100 ml of that water and toss vigorously over the heat for 30–60 seconds. The sauce becomes a glossy emulsion.

Salt pasta water noticeably: about 10 g salt per litre. It's the only moment pasta can absorb seasoning from the inside.

After searing meat, brown stuck-on bits remain on the bottom of the pan. That's not dirt — it's concentrated flavour, and the quickest restaurant sauce is made right on top of it.

Pour off excess fat, add 150 ml stock, wine or water to the hot pan and scrape up the bits with a spatula. Reduce the liquid by half. Take the pan off the heat and whisk in cubes of cold butter one at a time, swirling the pan. The butter doesn't melt into a puddle — it turns the sauce into a thick, glossy emulsion. The French call this 'mounting' with butter.

Light cream (around 10% fat) easily curdles when boiled with acidic ingredients (wine, tomatoes, lemon). For hot sauces use cream with 20% fat or more — the fat protects the proteins from curdling.

Add cheese at the end, off the heat or on the lowest flame. Grate parmesan as finely as possible and stir it in a handful at a time. Throw cheese into a boiling sauce and it seizes into a rubbery clump and releases oil.

Never sprinkle starch into hot liquid: it sets into lumps instantly. Always mix it with a little cold water first.

Pour the slurry into the simmering sauce in a thin stream, stirring constantly, and boil for 1 minute: starch only thickens fully after it boils, and the raw taste cooks off.

Milk sauces like béchamel use a roux — flour cooked in butter. Melt butter, add an equal weight of flour, cook for 1–2 minutes while stirring, then add cold milk in portions, whisking smooth each time.

Taste at the end and adjust with this cheat sheet: