01 - Preheat the oven to 350°F and line two baking sheets with parchment paper.
02 - Whisk together flour, cocoa powder, baking soda, salt, and cinnamon in a medium bowl.
03 - Using an electric mixer or whisk, cream softened butter with brown and granulated sugars until light and fluffy.
04 - Beat in eggs one at a time, then stir in vanilla extract until fully incorporated.
05 - Gradually blend the dry mixture into the wet ingredients until just combined.
06 - Gently fold in oats, raisins, and chocolate chips if using.
07 - Drop tablespoon-sized balls of dough onto prepared baking sheets, spacing about 2 inches apart.
08 - Bake for 11 to 13 minutes until edges are set and centers remain soft.
09 - Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.