First, weigh out and chill everything: dice the butter and put it in the fridge (the smaller the dice, the quicker and more evenly it will rub in. A few bigger chunks will help ensure those flakes so don’t worry too much as long as they're no more and 2-2.5cm big). Crack and beat the egg and chill that too. You can even chill the mixer bowl and flour if it's a warm day.
Place flour, sugar, salt and baking powder into stand mixer bowl, and mix briefly to combine.
Add the diced cold butter, and mix with the paddle attachment to rub the flour into the butter. Making sure the flour gets rubbed into fat is the key, you don't need to crumb/rub in all the butter. In fact, we want little pea sized or smaller bits of butter left.
Once all flour rubbed in and definitely before it starts to come together on its own, add the egg. It will take some time to fully form a dough, but don’t be tempted to add more liquid unless it's really clearly needed (different flours absorb liquid differently, so it's possible, but as you see in the vid, it's pretty crumbly as it comes together, then turns out perfect!).
Shape into discs (I normally form 2-3 for each 250g butter quantity of pastry) and flatten, then wrap in cling and chill for a least 4 hours or preferably overnight, before using. Flatter discs means less rolling and more tender pastry!
I always prep pastry 1 if not 2 days before I want to bake the pies. The high butter content means it really benefits from a good long chill between each stage. So make pastry, chill. Cut/shape pastry, then chill. Build pies, then chill before baking.
