Trying to make forgotten cookies (meringue cookies baked in oven over night)

Maybe i misspoke in my first sentence. If they were truly runny and had lost all form, i prob would have spread the deflated meringue in a parchment paper lined sheet or cake pan and figured if the results were edible, it would be for just family, or good for crumbling over ice cream. Meringue, when spread out and baked as a solid layer in a cake pan, for instance, can make a lovely base for a layered dessert of mousse, ganache, buttercream, ice cream, or whatever.

Oh, I'm sorry I didn't see this before now. Do you have a gas oven? I'm on my third, and none of them have held the heat well enough to truly make "forgotten" cookies. I keep my pizza stone in the bottom of the oven at all times. That helps the temperature stay fairly even. (better than without) when I make meringues, I keep the temperature at the lowest setting (170 on my oven). It takes 3-4 hours for the meringues to completely dry.

sorry about that; i would have baked them anyway. In the future, here's how i dealt with that problem when i made pecan meringue cookies (mine did NOT have to stay in the oven overnight.):
I whipped the room temp egg whites with a pinch of salt once they started to go opaque, and then added the sugar after they went opaque white, til the mixture was stiff and glossy and peaks stood straight up. When you add something fatty like ground pecans, the fat starts to deflate the meringue v quickly. So my solution was to
remove only as much meringue as i could handle/shape QUICKLY , on 1-2 parchment-covered sheet pans. To this amount of meringue I folded in the pecans, piped this batch and baked immediately. When they had baked, I repeated the process. This way, you don't have some of your meringue sitting a long time with the pecans already folded in, which will quickly get them weeping. BTW, there is a good mint chip meringues recipe in one of the Silver Palate cookbooks.

I'm not an expert baker but I see your question is urgent. I have never been able to rescue fallen egg whites. I would guess the additions overwhelmed the whites. Sounds like a lovely recipe.