Brookies

Instructions

1. 1

   Heat the oven and line the pan

   Set a rack in the center of the oven and heat to 350°F. Line a 9x13-inch metal pan with parchment, letting it hang over the two long sides so you can lift the whole slab out later. Metal is worth seeking out here; glass holds heat differently and will leave you with gummy corners.

2. 2

   Build the brownie batter

   In a large bowl, whisk the melted butter with both sugars until the mixture looks like wet sand, about 30 seconds. Add the eggs one at a time, whisking hard after each, then the vanilla. Keep whisking for a solid minute after the last egg goes in. This is what dissolves the sugar and gives you that thin, papery, crackly top, so don't rush it.

3. 3

   Finish and spread the brownie layer

   Sift the cocoa powder over the bowl, add the flour and salt, and fold with a spatula just until no dry streaks remain. Fold in the chocolate chips. Scrape the batter into the pan and spread it flat with an offset spatula, pushing it into the corners. A level brownie layer is what keeps the bars from baking unevenly.

4. 4

   Make the cookie dough

   In a second bowl, beat the softened butter with both sugars on medium speed until pale and fluffy, 2 to 3 minutes. Beat in the egg and vanilla, scraping the bowl. Add the flour, baking soda, and fine salt, and mix on low just until the flour disappears. Fold in the chocolate chips by hand.

5. 5

   Patch the cookie layer on top

   Pull off pieces of dough about the size of a golf ball, flatten each between your palms into a rough disc, and lay them over the brownie batter like paving stones. Don't spread the dough with a spatula, you'll just drag the brownie up into it. Pinch the seams together with your fingers, leaving a few gaps where the brownie can peek through. Scatter the flaky salt over the top if using.

6. 6

   Bake

   Bake 34 to 38 minutes, until the cookie layer is golden at the edges and set but still soft in the center, and the brownie puffs slightly at the sides. If the top is browning fast before the center sets, tent loosely with foil for the last 10 minutes. A skewer poked into the middle should come out with moist crumbs and a little melted chocolate; wet, raw batter means give it 4 more minutes. These are far better slightly underbaked than over.

7. 7

   Cool completely before cutting

   Let the pan cool on a wire rack for at least 2 hours. I know. But the brownie layer is still liquid under there when it comes out of the oven, and cutting early turns clean squares into a smear. Once fully cool, lift out by the parchment and cut into 24 bars with a long knife, wiping the blade between cuts.

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Baker's Tips

• 1.

  Weigh the flour if you can. An extra 20 grams scooped into the cookie layer is the difference between chewy and dry, and it's the single most common reason brookies disappoint.

• 2.

  The two layers have different doneness windows, which is the whole challenge of this bake. Trust the brownie, not the cookie: a cookie top that looks a touch underdone is correct, because it keeps setting as the pan cools.

• 3.

  For cleaner layers, chill the assembled pan 15 minutes before baking. The cookie dough firms up and sinks less into the brownie batter.

• 4.

  Chopped bar chocolate instead of chips in the brownie layer gives you melty pools and shards rather than uniform dots. Worth doing at least once.

• 5.

  Bringing the eggs to room temperature matters more than it sounds. Cold eggs seize melted butter and you'll get a greasy, separated brownie batter.

• 6.

  Toasted walnuts or pecans, about 3/4 cup, can be folded into the brownie layer without any other adjustment.

Equipment

• 9x13-inch metal baking pan
• Parchment paper
• Electric mixer (stand or hand)
• Two large mixing bowls
• Whisk
• Offset spatula
• Rubber spatula
• Wire cooling rack
• Kitchen scale (recommended)

Storage