I’ve not made a crust with egg (at least I don’t remember), so I’m not sure how that factors in, if at all. Over processing is easy to do if you don’t just pulse the fp. I actually prefer using a pastry blender. You want some gluten development but not too much. If you started rolling the dough when it was too cold, it can crack/break. Your ratio of flour to fat doesn’t sound too off. My go-to crust (Martha Stewart’s Pate Brisee) calls for 2 1/2 cups flour and 1 cup butter. I often make it with part butter/part shortening for optimum texture and flavor.

ETA - I see online one site mentions the egg can make the crust more pliable and compact. My own experience is an egg isn’t needed for pliability, and I’m not sure I’d want the crust to be compact. Let’s see what others can suggest for your questions.

Lots of good thoughts, but there are huge differencesxin ingredients, and that might be a factor too. The water content of butter is really noticeable in pastry, as is the protein contect of the flour. If you meant Crisco shortening, it's a totally different formulation than before 2p years ago. Even the size of eggs has changes, but from many more decades ago. You could scale for one crust and try making it by hand to see how things go.

The spoon to cup method is lovely for cakes, but do you think your MIL did it? Do you think she sifted? I'd guess, unless she only recently passed, that it's most likely dip/level/pour. Dipping in too narrow a canister can compact the flour, which is why they push the spoon method now, because the container doesn't matter.

I don't know what happened to your pastry, but in addition to the sciencey stuff, there's also the bad fairy cursed it that sometimes happens. Oh! And the weather.

I use vodka instead of vinegar, and here are the proportions I use when I add an egg:

1 cup whole wheat flour
4 cups unbleached bread flour
1 tsp salt
1/4 cup sugar
1-1/2 cups cold unsalted butter (3 sticks), cut into 1/4-inch slices
1 cup chilled solid vegetable shortening , cut into 8 pieces
1/3 cup cold water

1 egg, beaten

1/3 cup vodka

I have a total of 5 cups flour and a total of 2-1/2 cups fat (shortening plus butter). I have 2/3 cup liquid (not counting the egg), which is similar to yours, but then I always add a bit more water, as I like to start off with a bit less than I really need. I use half as much salt but more sugar, but that is more for taste.

I do not allow the dough to come to room temperature before rolling it out - I roll it out when it is as cold as possible, but you would need more fat in the dough for this to work.

Overworking the dough is always bad, and at this point, I do not see how to make it into a regular pie crust. However, you could make it into a crumble topping, like what is used for cobblers. Add more sugar plus some butter if you want to do that, but don't work these into the dough, if possible.

I use a recipe posted by Islay Corbel a long time ago. It’s fiddly to roll, but the finished product is the pastry I’ve been looking for all my adult life!

Too much shortening wouldn't make a dough that separates and falls apart, I think - wouldn't it be oily and soft and maybe sticky to work with?

If you want an easy pie crust recipe, the one from the book Cooking With Gourmet Grains, published by the Orowheat Bakery is the simplest:

For one crust:

1/2 cup butter, softened

1/2 cup cottage cheese

1 cup flour

Beat the butter and cottage cheese together and mix in the flour. Form into a ball and chill slightly before rolling out. No salt needed because there is enough in the cottage cheese, but you might want to add some if you use unsalted butter.

If you are going to bake this crust before filling it, you will need to prick the dough and use pie weights with parchment or foil, as it will puff up too much otherwise.

The recipe has too little shortening/butter.....

My recipe is 1 1/2 cups AP flour...fluffed! (175 to 180 grams)

1 stick of frozen butter cut into half inch cubes 2/3 tsps salt

Pulse in Food processor until like split pea size. Add 2 shots of vodka and pulse maybe 5 times, dump into a bowl and dribble ice water into it tossing with a fork until it can form a ball...

Make a flat disc, wrap well in saran and refrigerate art least an hour....over night is better....

Roll out....makes one 10 inch crust....can eb doubles.

No sugar, no egg, and above all no oil!!

I always use the original Crisco crust recipe. Works everytime.

I have been using Nathan's Never Fail Pastry since it was first posted by Canarybird years and years ago. I use half butter and half lard. For the few pies I make each year, I overlook the lard! It truly has never failed for me and if baked long enough, produces and almost puff pastry texture.

nekotish, you reminded me of my grandmother’s pie crust. I don’t have the recipe but it was truly one of the best. Made with hot water and lard.

I tried lard once, but I did not like the taste.

I don't have a 'best pastry' recipe. It depends on what I'm making. The different types, short crust, hot water crust, sweet pastry, enriched etc. are for different purposes. Lard, or lard and butter is excellent in a short crust for a savoury pie. Hot water crust is classic for a raised pie. Sweet crust is used by a lot of people in desserts but personally I like the crust to be a foil for a sweet filling, not yet more sweetness. Oil also has its uses.

lars' cottage cheese recipe is my go to ...