I've made these quiet a few times because they are SO easy and use so few ingredients. My sister says they taste like M&Ms :P They're really chewy and chocolate-y and epic.
I use this recipe. I use chocolate chips instead of nuts, though. I also usually halve the recipe because the cookies are pretty big. You also really cannot put more than 3-4 on a cookie sheet, as they spread a TON. I would imagine they'd keep well for a few days in an airtight container, but they've never lasted that long in my house.