How does the number of eggs affect a cookie recipe?
Eggs contribute to better texture, leavening and they extend shelf life. More eggs = moister (sp!) cookie. Eggs are also crucial in building structure. They are about 75% moisture, 12% protein, 10% fat and 2ish % sugar.
The white provides strength, stability and moisture.
Yolks, where all of the fat is in an egg, increase richness, tenderness and flavor.
Therefore, if you put an extra egg, you will get a chewier cookie. I do it all the time. If you put less, you will get a more crumbly cookie.
Another trick is to use extra large or jumbo eggs, even though most recipes call for large. There is only about 10-15% more egg 'stuff' per egg, but it can make your baked goods a little moister without making the dough too gooey. My mother does this all the time, and we all know Mom's cookies are the best. I usually just have large eggs around the house for various reasons, but using larger eggs has never been a problem in my experience.
My take is that eggs will promote a SOFTER cookie, not necessarily a CHEWIER cookie. Soft cookies and chewy cookies are not the same. Soft means a slightly more cake-like texture. Chewy has more substance to it; takes longer to chew! Neither is crumbly or hard. I wonder if others agree.
The more eggs, the more cakelike a brownie or cake recipe will become.
The less eggs, the more moist and dense it will be.
Eggs cause fluffiness.
Nope. Whipped egg whites (or even whipped whole eggs, to some degree) add fluffiness, sure. But just stirred/beaten into the other ingredients? They add fat and moisture, and they're not adding any air. They're not going to make a cookie fluffy.
and generally in cookies, flour contributes to a cake-like texture. Whole eggs generally make a cookie chewier.
This is not a forum, answers should be standing on their own ground to the original question, not interjections against other answers.
@LarsViklund Yes, it starts with "wrong" and obviously was replying to something. But it also makes a specific claim about what the answer to the question is (eggs make things cakelike and fluffy), so it is also certainly an answer.