Rub in

To rub in means to mix cold fat into flour by rubbing them between your fingertips. The fat breaks into tiny pieces coated in flour, and the mix ends up looking like fine breadcrumbs. It is the first step for shortcrust pastry, scones (biscuits in the US), crumble toppings and many simple cakes. American recipes often do the same job with a tool and call it cut in.

How to do it

1. Cut cold butter into 1 to 2 cm (½ inch) cubes and add it to the flour.
2. Toss the cubes so they are coated in flour.
3. Pick up some flour and butter with the tips of your fingers and thumbs.
4. Rub them together lightly, letting the mix fall back into the bowl. Lift your hands up a little as you go to let air in.
5. Shake the bowl now and then to bring larger lumps to the top.
6. Keep going for 3 to 5 minutes until no large lumps of butter are left.

How to tell it is done

The mix looks like fine breadcrumbs or sand. When you squeeze a handful, it clumps, then breaks apart again. For a flakier pastry, stop a little earlier with some small, flattened flakes of butter left.

Why it works

Coating flour in fat waterproofs part of it, so less gluten forms when you add liquid. That gives a tender, crumbly texture, which bakers call "short". Fingertips are the coolest part of your hand, so the butter stays solid. Lifting the mix adds air and keeps it light.

Common mistakes

• Using your palms. They are warm and melt the butter into a greasy paste.
• Using soft butter. Same problem. Keep it in the fridge until the moment you start.
• Rubbing too long. Once the mix turns oily or clumps into a dough without liquid, the result will be hard. Chill it for 15 minutes and finish gently.
• Adding all the liquid at once afterwards. Add it a little at a time until the dough comes together.

In recipes

"Rub the butter into the flour until the mixture resembles fine breadcrumbs" is the classic British phrase. A food processor gives the same result with short pulses.