This doesn;t make it less crumbly but makes rolling out easier in that the edges don;'t tend to split out and make a sort of scallop when the edges are dry:
Before rolling, i flatten the dough and make the edges slightly thicker than the middle. I form it with my hands so that it doesn;t begin cracked, but the sides are nice and compact using a little pressure.
Then when i begin rolling with the rolling pin, I only roll to within an inch of the edge, from the center to 1 inch from edge, then turn roughly 1/6th of a turn, then roll out to within 1 in from edge, then turn again about a sixth, then again to within one inch. etc. all around and around till it;s the thickness i want.
That way you keep the edge slightly thicker than the center, and it cracks less. I sometimes press hard around the edge if i see it cracking, or fold under a bit to keep it thicker till i get to the last rolling, when it will usually have compressed enough not to crack much. (The compression slightly softens the butter, making it moister, without melting it).
Of course, when you make the dough, it might just be necessary to add a little water. Whatever the recipe is, since there is a variation in flours and butters, you might need to adjust. My eyeball method is this: I make a ball from the dough and then try to crack it open. If it cracks really easily and crumbles a bit, i recrumble the whole thing, wet my hand so it's dripping and shake it over the dough. Then toss it lightly and make a ball again. If it crumbles already in the ball stage, you're going to have trouble rolling and also even making it hold together when you lay it in the pie dish. You have to be careful you don;t overwork it, but the crumbling and tossing doesn;t ruin the flakiness of the final product. Also when you try to break the ball if it crumbles into a lot of pieces, you'll need a couple of wet hands' worth of water sprinkled over the dough before tossing and reforming it. No point doing it many times, it would need more water.
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