Ingredients
Equipment
Method
- Position the oven rack in the middle slot and heat the oven to 350°F (175°C), then grease an 8x8 inch (20x20cm) light-colored ceramic or aluminum baking dish thoroughly with unsalted butter, covering the bottom, all four sides, and the corners.
- In a large mixing bowl, whisk together 1 cup (125g) all-purpose flour, ¾ cup (150g) plain white granulated cane sugar, ½ cup (40g) natural unsweetened cocoa powder, ½ tsp (2g) baking powder, and ½ tsp (3g) fine sea salt with 20 to 25 wide circular strokes until the color looks completely even with no pale flour patches or dark cocoa streaks.
- Make a well in the center of the dry ingredients and add 2 large room-temperature eggs, ½ cup (113g) unsalted butter melted and cooled to below 90°F (32°C), and ½ cup (120ml) room-temperature whole milk directly into the well — confirm the butter is below 90°F (32°C) before adding the eggs.
- Using a silicone spatula, fold the wet and dry ingredients together with slow deliberate strokes from the bottom of the bowl upward, counting 20 to 25 strokes, and stop the moment no dry flour streaks remain — the batter should be thick, dense, and paste-like, dropping heavily from the spatula rather than pouring.
- Scrape the entire batter into the prepared baking dish and use the flat face of the spatula to spread it from the center outward toward each edge and corner until the surface looks roughly even and the batter reaches all four corners.
- Scatter 1½ cups (255g) semi-sweet chocolate chips evenly across the entire surface of the batter in rows from one edge to the other so the chips cover nearly every square inch — do not press them into the batter.
- Bake on the middle rack at 350°F (175°C) for 25 to 27 minutes without opening the oven before the 23-minute mark, then gently press the center with one finger — the surface should feel set and resist your finger while the center still feels soft, and the chips should look melted and glossy; if the center still feels liquid, add 2 minutes and recheck.
- Remove the pan from the oven, set it on a wire rack, and rest for exactly 10 minutes before scooping warm directly from the pan — or cool fully for 45 to 60 minutes before cutting into 9 squares with a sharp knife wiped clean between each cut.
Notes
- Flour: Spoon into the measuring cup and level — never scoop directly from the bag. Scooping packs 20–30% more flour and produces a dry, dense cake. Weigh at 125g for best results.
- Cocoa powder: Use natural unsweetened cocoa only — not Dutch-process. Dutch-process does not react with the baking powder correctly and produces a flat, milder cake.
- Butter: Must be melted and cooled to below 90°F (32°C) before the eggs go in — hot butter will scramble the eggs on contact.
- Chocolate chips: Use semi-sweet chips in the 45–55% cacao range. Milk chocolate is too sweet; chips above 60% cacao will set firmer and taste sharper than what is shown in the photos.
- Baking powder: Test freshness before baking — drop 1 tsp (4g) into ½ cup (120ml) hot water. It should bubble immediately. Replace if the reaction is weak.
- Pan size: Tested in an 8x8 inch (20x20cm) pan. A 9x13 inch pan spreads the batter thinner — reduce bake time to 18–20 minutes. A dark non-stick pan absorbs more heat — reduce oven temperature by 25°F (15°C).
- Doneness: Use the press test, not the toothpick. Pull the cake when the surface resists gentle pressure but the center still feels soft. A clean toothpick means the cake is overbaked.
- Storage: Cover tightly with plastic wrap pressed onto the surface. Room temperature up to 2 days. Refrigerate cut squares in a lidded container with parchment between layers up to 5 days. Reheat at 50% microwave power in 20-second increments.
- Freezing: Wrap individual squares in plastic wrap, freeze up to 2 months. Thaw overnight in the refrigerator — do not thaw at room temperature. Reheat at 50% microwave power in 20-second increments.
- Scaling: To double, bake in two separate 8x8 inch pans — do not increase the depth of one pan. Use 1 tsp (4g) baking powder total across the doubled batch — leavening does not scale linearly.
- Altitude: Above 3,500 feet (1,065m), reduce baking powder to ¼ tsp (1g), increase flour by 2 tbsp (16g), and bake at 375°F (190°C).
- High altitude bakers: See the FAQ section for full adjustment guidelines specific to this recipe.
- Allergens: Contains gluten, eggs, dairy, and soy (chocolate chips). Check chip labels for soy lecithin if soy is a concern.
- Make-ahead: Measure and combine dry ingredients up to 3 days ahead. Add wet ingredients on baking day — do not mix the full batter ahead of time.