01 -
Preheat oven to 175°C. Grease a 33 x 23 cm baking pan with butter, line with parchment paper leaving an overhang on two opposite long sides, and grease parchment with butter.
02 -
In a medium heatproof bowl set over a pot of barely simmering water, melt chocolate and butter together, stirring until smooth, about 3 minutes. Allow to cool slightly.
03 -
In a large bowl, whisk together eggs, granulated sugar, cocoa powder, vanilla, and salt until smooth. Whisk in chocolate mixture, then fold in flour until just combined. Spread batter evenly in prepared pan.
04 -
In a medium bowl, whisk flour, baking soda, and salt. Using a handheld mixer on medium-high speed, beat butter, brown sugar, and granulated sugar until light and fluffy, about 3 minutes. Beat in egg and vanilla, then reduce speed to low and add dry ingredients, mixing until just combined. Fold in chocolate chips.
05 -
Scoop 12 mounds of cookie dough over brownie batter in pan. Cover with foil.
06 -
Bake covered for 55 minutes. Uncover and bake an additional 5 minutes until golden and a tester inserted comes out with moist crumbs. Transfer pan to wire rack and cool completely.
07 -
Run a knife along pan edges, then lift brookie slab using parchment overhang onto a cutting board. Cut into 12 bars, then slice each bar in half horizontally.
08 -
Let ice cream soften for 5 to 10 minutes. Spread ice cream over cut sides of half the brookie bars, then top with remaining halves, cut side down. Arrange on a freezer-safe tray, wrap with plastic, and freeze at least 30 minutes until firm.
09 -
Before serving, allow sandwiches to soften for 10 to 15 minutes at room temperature for optimal texture.