Brown Butter Brookies: Gooey Cookie Base, Fudgy Brownie Crown Step-by-step instructions

Before you start

Heat the oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment paper, leaving an overhang on two sides for easy lifting. Measure all ingredients before starting.

Brown the butter first and let it cool while you measure the dry ingredients. Make sure the eggs are at room temperature for a smoother batter. Have a wire rack ready for cooling.

Instructions

Prep and Assemble

1. 1Brown the Butter and Mix the Cookie Base
   Melt the butter in a small saucepan over medium heat. Cook, swirling occasionally, until the butter turns deep golden brown and smells nutty, about 5 to 7 minutes. Pour the brown butter into a large heatproof bowl and let it cool for 10 minutes. Whisk in the granulated sugar, brown sugar, eggs, and vanilla until the mixture is smooth and glossy. Stir in the flour, baking soda, and salt until just combined, then fold in the chocolate chips. The dough will be thick and slightly sticky.
   Look for The butter should be amber and smell toasted, not burnt. The cookie dough should hold together when pinched but not be overly dry.
   Tip Cool the brown butter completely to avoid scrambling the eggs. If the butter is still hot, let it sit longer before adding the eggs.
2. 2Make the Brownie Batter
   In a separate bowl, whisk the cocoa powder, flour, baking powder, and salt. In another bowl, whisk the melted brown butter (reserved from the cookie layer) with the granulated sugar and brown sugar until combined. Add the eggs and vanilla, whisking until the batter is thick and glossy. Stir in the dry ingredients alternately with the milk, starting and ending with the dry ingredients. The batter will be thick and fudgy. Pour the brownie batter over the cookie base in the pan, spreading it evenly to the edges.
   Look for The brownie batter should be dark, glossy, and thick enough to hold its shape when dropped from a spatula.
   Tip Use a small offset spatula to spread the brownie batter gently over the cookie layer without disturbing it.

The brown butter should be amber and smell nutty. The cookie dough should be thick and studded with chocolate chips.

The brownie batter should be glossy and thick. When spread over the cookie base, the two layers should stay distinct without blending together.

Bake and Cool

3. 3Bake the Brookies
   Heat the oven to 350°F (175°C). Place the assembled pan on the middle rack and bake for 30 to 35 minutes, until the top is set and a toothpick inserted into the center comes out with a few moist crumbs. The brownie layer should look crackly and the edges should be slightly pulling away from the pan. The cookie base will be golden and firm. Remove the pan from the oven and place it on a wire rack.
   Look for The top should be glossy and cracked, and the edges should be set. A toothpick inserted into the center should come out with moist crumbs, not wet batter.
   Safe temperature 160°F (71°C) internal temperature (egg dishes)
   Tip Do not overbake; the brownie layer will continue to set as it cools. The residual heat will firm the cookie base.
4. 4Cool Completely
   Let the brookies cool in the pan on a wire rack for at least 2 hours. This allows the layers to set and the flavors to meld. Do not slice while warm, or the bars will crumble. Once completely cool, use the parchment paper to lift the entire slab out of the pan. Place it on a cutting board and slice into 16 thick bars with a sharp chef's knife. Wipe the knife clean between cuts for neat edges.
   Look for The slab should be completely cool to the touch, and the top should feel firm. The bars should cut cleanly without crumbling.
   Tip For extra-clean slices, chill the slab in the refrigerator for 30 minutes before cutting. This firms the layers and makes the bars easier to handle.

The top should be crackly and set, and the edges should be pulling away slightly from the pan. A toothpick inserted into the center should come out with moist crumbs. The kitchen will smell of toasted butter and chocolate. Cool completely before slicing.

Slice and Serve

5. 5Slice and Serve
   Slice the brookies into 16 equal bars, each about 2 inches wide. Serve at room temperature or slightly warm for a gooey texture. The bars can be stored in an airtight container at room temperature for up to 3 days. For longer storage, wrap individually and freeze for up to 3 months. Reheat in a 300°F oven for 5 minutes to refresh the texture.
   Look for Each bar should have a visible two-layer structure: a chewy cookie base and a dense brownie crown.
   Tip For a bakery-style finish, sprinkle a pinch of flaky sea salt on top before serving.

The slab should be firm and cool to the touch. Slicing should yield clean, neat bars with a visible two-layer structure. The cookie base should be chewy, and the brownie crown should be dense and fudgy.

Common mistakes

Overmixing the cookie dough can make it tough, so mix until just combined. Do not overbake the brookies—they will continue to set as they cool, and overbaking will dry them out.

Make sure the brown butter is not too hot when adding eggs, or the eggs will scramble. Spread the brownie batter gently over the cookie base to avoid mixing the layers. Finally, wait until the bars are completely cool before slicing to get clean edges.

How to tell it’s done

The brookies are done when the top is set and a toothpick inserted into the center comes out with a few moist crumbs, not wet batter. The edges will be slightly pulling away from the pan, and the brownie layer will have a crackly, glossy surface.

The internal temperature of the eggs should reach 160°F (71°C) to ensure they are fully cooked. Let the bars cool completely before slicing to allow the layers to set.

• Egg dishes: 160°F (71°C) in the thickest part