Preheat oven to 350° F. Line baking sheets with parchment paper or silicone baking mat and set aside.: As the oven warms, you should feel the kitchen gradually get cozy and notice a faint warm air when you crack the oven door slightly. Preheating to 350° F ensures instant oven spring and even baking, which helps form those slightly crisp edges while keeping the centers tender. Lining the sheets with parchment or a silicone baking mat prevents sticking and encourages gentle browning on the bottom. A common mistake is not allowing the oven to fully reach temperature, resulting in underbaked centers and overspread cookies, so use an oven thermometer if your oven fluctuates.
In large bowl, cream butter and sugars together until light and fluffy. Stir in egg, vanilla, peppermint extract and milk. Scrape the bowl and mix again.: When creaming, you will hear a soft whipping sound as the butter and sugars aerate, and the mixture will lighten in color to a pale, slightly glossy texture. This aeration traps tiny air bubbles that give lift and tender crumb. Adding the egg , vanilla , peppermint extract , and milk will loosen the mix into a silky batter; after each addition, scrape the sides so nothing remains unmixed. If you overmix at this stage, the dough can become too airy and collapse, so stop once everything is homogenous and smooth.
Stir in all dry ingredients until just combined. Scrape sides and bottom of bowl to ensure batter was evenly mixed.: As you fold in all purpose flour , cocoa powder , baking soda , and salt , you will notice the dough darken and thicken to a scoopable consistency. The goal is to stop mixing as soon as streaks disappear, preserving tenderness. Overworking the dough develops gluten and yields tougher cookies, so fold gently until the dry bits are fully moistened. A frequent error is using a mixer on high, which can lead to dense, chewy cookies instead of tender ones.
Stir in chocolate delightfuls by hand using a rubber scraper.: Folding in the Nestle Tollhouse Dark Chocolate Mint Delightfuls by hand keeps the chunks intact and distributes pockets of melty chocolate throughout. You should see flecks of minty chocolate dotting the dough, and the effort will be quiet and tactile as the scraper glides through. Using a scraper helps prevent overmixing and keeps the dough at the right consistency. Avoid using a paddle at high speed which can pulverize the pieces and change texture.
Scoop onto prepared baking sheets and bake 8-9 minutes. Remove from oven and cool 5 minutes before transferring to cooling rack.: As the cookies bake, watch for edges to set and small cracks to appear on top, signals that they are nearly done. At around eight minutes, they should still look slightly underbaked in the center, which is perfect for a soft interior. The short cooling on the sheet allows them to finish cooking gently and firms them enough to transfer, while still preserving chewiness inside. A common misstep is leaving them in too long; they will crisp up but lose their plush center if overbaked.
Drizzle the tops with melted chocolate chips. Sprinkle with crushed candy canes. Enjoy!!: The glossy melted semi sweet chocolate chips will drip and set into delicate ribbons across the warm cookie tops, and the crushed candy canes add a bright, crunchy contrast that crackles as you bite in. Work while cookies are warm so the drizzle adheres, then let them cool fully so the chocolate firms. One thing to avoid is applying candy canes while the chocolate is still liquid on very hot cookies, which can cause the candy to melt slightly into the chocolate and lose its crispness; wait a few minutes if the cookies are piping hot.