01 - Preheat oven to 350°F and line two baking sheets with parchment paper.
02 - Whisk together flour, cocoa powder, baking powder, baking soda, and salt in a medium bowl. Set aside.
03 - Beat butter, granulated sugar, and brown sugar in a large bowl until light and fluffy, about 2-3 minutes.
04 - Add eggs one at a time, beating well after each addition.
05 - Mix in milk, vanilla extract, white vinegar, and green food coloring until fully combined.
06 - Gradually add dry ingredients to wet mixture, mixing until just combined. Avoid overmixing.
07 - Drop dough onto prepared baking sheets using a cookie scoop or tablespoon, spacing 2 inches apart.
08 - Bake for 10-12 minutes until edges are set but centers remain soft.
09 - Let cookies cool on baking sheets for 5 minutes, then transfer to wire rack to cool completely.
10 - Melt white chocolate with oil if using in microwave-safe bowl in 20-second bursts, stirring until smooth.
11 - Drizzle melted white chocolate over cooled cookies using fork or piping bag. Allow to set before serving.