I love a lot of cookies, including big dire American cakey chocolate creations, but the cookies that I love the most are those on the superficially more boring end of the spectrum. Thin crisp buttery cookies, various shades of blond and tan. Oblaten, cialde, gaufrette, pizzelle, langues de chat, tuile, fortune cookies, plain stroopwaffles, Pepperidge Farm Chessmen. I buy and eat empty ice cream cones. I love the cookie sticking up out of a sundae more than the sundae. If there are lightly browned edges, I like it.
My current crisp buttery cookie obsession are crepes dentelles from Brittany. The ones most commonly sold in the US seem to be Gavottes, which in their (dark- or milk-) chocolate-covered state are the most insanely delicious cookies I know and almost impossible to stop eating.
Even happier, when you crush up crepes dentelles they become feuilletine, crisp flakes used to make other pastries and desserts, or sometimes into a thin bark when coated in chocolate and then broken up. Leonidas makes a feuilletine chocolate bar I am dying to try.
This photo shows a man in Brittany making crepes dentelles (makes it clearer how they're shaped) and this video shows chefs making them in a slightly different shape for a napoleon.
My favorite cookbook, The French Cookie Book, seems to have no recipes for these particular cookies. I don't know know why; perhaps because they've been produced industrially more than in patisseries. The book is great, though. It's very different from many contemporary pastry recipes/books. This book covers over 500 pages of recipes that differ primarily in technique and tradition, not ingredients. Which is to say, every possible kind of crisp buttery cookie. It's an amazing reference.