These cookies deliver big flavor because the key ingredients get special attention. We toast both the oats and pecans to coax out their nuttiness, then grind the oats in a food processor so the finished cookies have a more refined texture than your standard oatmeal cookie. The butter is deeply browned to add deep, butterscotchy notes that carry flavor throughout the dough. Chunks of bittersweet chocolate create pockets of gooeyness, while finely chopped milk chocolate lends creaminess and milky sweetness that melts into the cookies. (You can use store-bought chocolate chunks sold in bags alongside the chocolate chips, or chop your own from a bar. And you can grate the milk chocolate on a box grater if you find that easier than finely chopping it.) The recipe doubles easily, and the portioned dough can be frozen up to a month. Bake the cookies directly from the freezer, without thawing, for 20 minutes, rotating the baking sheet halfway through.