Making a moist cookie
What are the secrets to making a very moist cookie?
I find that with chocolate chip cookies (the only kind I make), you have to undercook them a little bit, I try to pull them out of the oven about a minute before they look done, they will look a bit underdone but they firm up as they rest on the counter. Also, make sure you remove them from the hot baking sheet or they will continue to cook and the bottoms will get too crisp.
I'm not sure there are any secrets but there are a lot of variables. A couple of things I've learned is that more sugar can produce a moister cookie, depending oh how long it bakes, but it also tends to produce a cookie that flattens out into a thinner cookie than I might want. If I melt the butter before adding it to the flour mixture I get a moister cookie. If I use oil or shortening, instead of butter, I get a moister cookie. I find that I get a higher moisture result in cookies when using brown sugar or sweetening ingredients in that family (e.g. molasses) because those are so hygroscopic. Honey acts much the same way.
Using brown sugar will make a difference (for chocolate chip coookies). How the butter is will make a difference as well. Room temp as opposed to melted, as opposed to melted and cooled, and as opposed to heated until water has been eliminated and then cooled. Experimentation works, and if there are kids around, they will eat any "failures".
Butter. Works most of the time.
Apparently the only cookie anyone here thinks you might be contemplating is chocolate chip. Is that what you want to ask -- How can you make a chocolate chip cookie that is very moist, or some other kind of cookie that you have in mind?