01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper to prevent sticking and ensure easy cleanup.
02 - Place the butter in a medium saucepan over medium heat. Cook, stirring constantly, until the butter foams and develops a deep golden brown color with a nutty aroma, approximately 4-6 minutes. Remove from heat and allow to cool for 10 minutes.
03 - In a medium bowl, whisk together the flour, oats, baking soda, salt, and ground cinnamon until evenly distributed.
04 - In a large bowl, combine the cooled browned butter, brown sugar, and granulated sugar. Beat until thoroughly incorporated. Add eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing until just combined. Avoid overmixing to prevent tough cookies. Gently fold in chocolate chips or raisins and nuts if desired.
06 - Drop rounded tablespoons of dough onto the prepared baking sheets, leaving approximately 2 inches between each cookie to allow for spreading during baking.
07 - Bake for 10-12 minutes, or until edges turn golden brown and centers appear slightly set. The cookies will continue to firm up as they cool.
08 - Let the cookies rest on the baking sheets for 5 minutes before transferring to a wire rack to cool completely. This ensures proper texture development.