Preheat the oven to 350°F (175°C) and line a 9x9-inch metal baking pan with parchment paper.
Melt 10 tablespoons salted butter in the microwave in a micrwoave-safe bowl in 20-second increments until fully melted. Pour into a large mixing bowl. Whisk in 1 cup granulated sugar by hand until smooth, 30 seconds.
Add in 2 large eggs and 2 teaspoons vanilla extract. Whisk vigorously for 1 minute to ensure a crackly top.
Melt 1/2 cup chocolate chips in a microwave in 30-second increments, stirring between each. Once melted and smooth, whisk into the brownie batter until combined and smooth.
Use a rubber spatula to stir in 3/4 cup all-purpose flour, 1/4 cup unsweetened cocoa powder, and 1/2 teaspoon salt until just combined. Stir in whole, unmelted chocolate chips.
Pour into prepared pan and smooth out.
Bake in the preheated oven for 30 minutes. Let cool in pan 30 minutes before slicing.
Video
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Notes
Pan Options: A 9x9-inch light metal pan is best for crispy edges and fudgy centers; add 5–10 minutes for glass or ceramic pans and lower the temperature by 25°F for dark metal pans.
Double Batch: Use a 9x13-inch pan, double the ingredients, and bake at 350°F for 35–40 minutes.
Mix-Ins: Stir in 1/2 to 1 cup of chopped nuts, M&Ms or other candy, or chopped candy bars.
Swirls: Use 1/3 cup of peanut butter, Nutella, or caramel; drop spoonfuls over the batter and swirl gently with a knife.