It helps to bind the pastry ingredients together it also adds moisture and richness to to the mixture.
Egg in the pastry for richness and for the wetness to it is useable Egg in the filling to set the filling so it is not runny
To give the pastry substance and body.
as a binding agent
Yes, but they are not vegan.
Fat and taste i think
make the cake rise
it puffs the product
FLOUR provides the structure
The traditional ingredients used in making shu pastry are flour, butter, water, and eggs.
it helps the ingredients to stick together
mainly flour, eggs, water occasionally milk
It is just there for flavor, it has no effect on the flakiness.