01 - Preheat oven to 350°F. Line an 8x8 inch baking pan with parchment paper, ensuring edges overhang for easy removal.
02 - Whisk flour, cocoa powder, brown sugar, baking powder, and salt in a medium bowl. Pour in melted coconut oil, plant milk, and vanilla. Mix until just combined, then fold in chocolate chips.
03 - Evenly spread brownie batter across the bottom of the prepared pan using an offset spatula.
04 - Beat softened vegan butter, brown sugar, and granulated sugar in a separate bowl until fluffy and pale, about 2 minutes.
05 - Stir plant milk and vanilla into butter mixture. Add flour, baking soda, and salt. Mix until just combined, then fold in chocolate chips.
06 - Carefully spread cookie dough evenly over brownie batter. Lightly wet hands or spatula with water to prevent sticking.
07 - Bake for 30 to 35 minutes until top is golden brown. A toothpick inserted in center should emerge with moist crumbs, not wet batter.
08 - Cool completely in pan, approximately 1 hour. Lift out using parchment edges and cut into 12 equal squares.