Many oatmeal cookies are dry, cakey, and overly spiced. To make ours dense and chewy, we combine unsaturated fat (vegetable oil) and saturated fat (butter) in a ratio of nearly 3 to 1, and we reduce the proportion of flour. Adding an extra egg yolk boosts moistness and richness, while a touch more salt than most recipes call for tempers the sweetness and complements the oaty flavor. Most recipes call for using a stand mixer, but we found this counterproductive to our goal of chewy, dense cookies because the mixer beats air into the dough. Instead, we make our dough by hand, melting the butter for easier mixing. Browning the butter delivers more complexity and blooming a small amount of cinnamon in the butter rounds out its flavor. Raisins add pops of brightness and reinforce the chewy texture.
Regular old-fashioned rolled oats work best in this recipe. Do not use extra-thick rolled oats, as they will bake up tough in the cookie. For cookies with just the right amount of spread and chew, we strongly recommend that you weigh your ingredients. If you omit the optional raisins, the recipe will yield 18 cookies.