A friend of ours, who loves to bake — and especially with her grandchildren — forwarded this question to SavorSA after making cookies with the kids one day.
A. The art and science of cooking with eggs has filled many paragraphs in many chapters of books. We won’t go into the intricacies of the egg, or the chemistry of baking here. For the kids, the question has an easy, general answer: We add eggs to cookies for richness and moisture.
For an expert’s concise take on this question, we turn to Harold McGee’s “On Food and Cooking: The Science and Lore of the Kitchen”:
“Eggs generally provide most of the water in a cookie mix, as well as proteins that help bind the flour particles together and coagulate during baking to add solidarity. The fat and emulsifiers in the yolk enrich and moisten. The higher the proportion of whole eggs or yolks in a recipe, the more cakelike the texture.”
My paternal grandmother was an accomplished cookie baker and the recipe in the link below was our favorite. A plateful, with a plastic boxful standing by, was always awaiting us when we visited.