Hi Powderbrush!
You are asking about choux pastry, the dough that makes cream puffs, right? It’s a good question! Cooks used to working with gravies and the like are often confused by the “add all the flour at once” instructions in classic choux pastry recipes, but I can tell you that it does work and usually does not clump once the flour is worked in (although this might take a bit of elbow grease). I’m not really sure why, but it has something to do with the heat and proportions of water, butter and flour. I don’t think it’s a good idea to mix the flour and water beforehand – this is a tried-and-true French technique that has been used by chefs and home cooks for years.

You might want to try my Strawberry Peach Puffs recipe and give it a try!