Preheat and Prep:Set your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats to prevent sticking.
Cook Butter & Cocoa Mixture:In a medium saucepan, melt the butter with water over medium heat. Once melted, bring the mixture to a gentle simmer. Remove from heat and whisk in cocoa powder until smooth. Allow to cool slightly to prevent scrambling eggs.
Mix Wet Ingredients:In a large bowl, whisk together granulated sugar, eggs, and vanilla extract until creamy and light. Gradually pour the warm cocoa mixture into the sugar mixture, whisking continuously to blend evenly.
Combine Dry Ingredients:In a separate bowl, sift together flour, baking soda, cinnamon, and salt. Gradually add dry ingredients to the wet chocolate mixture. Stir just until combined—avoid overmixing to keep cookies tender.
Scoop and Bake:Drop tablespoon-sized portions of dough onto the prepared sheets, spacing about 2 inches apart. Bake for 8–10 minutes until edges are set but centers remain slightly soft.
Cool Cookies:Let cookies cool on the baking sheets for 5 minutes before transferring to wire racks to cool completely.
Prepare the Glaze:In a clean saucepan, melt butter over medium heat. Whisk in milk and cocoa powder until smooth. Remove from heat, then gradually whisk in powdered sugar and vanilla until glossy and pourable.
Glaze the Cookies:Spoon or drizzle the warm glaze over each cookie. Allow glaze to set for 10–15 minutes before serving.
