Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper.
In a microwave-safe bowl, melt the chocolate chips and butter in 30-second intervals, stirring between each, until smooth. Let cool slightly.
In a large mixing bowl, whisk together the sugar, eggs, and vanilla extract. Stir in the melted chocolate mixture until fully combined.
Add the green food coloring and mix until the batter is evenly colored.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually fold the dry ingredients into the wet mixture until just combined.
Pour the batter into the prepared pan and spread evenly. Bake for 30–35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Allow to cool completely.