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15x10 Inch Pan Brownies

15x10 inch pan brownies

Large batch of thin brownies baked in a 15x10 inch pan.
Course Dessert
Cuisine American
Keyword 15x10 inch pan, Thin Brownies
Prep Time 10 minutes
Cook Time 35 minutes
Total Time 45 minutes
Servings 24
Author Anna
Cost 5


  • 230 grams unsalted butter, cut into chnks (2 sticks)
  • 230 grams semisweet or bittersweet chocolate, chopped (half a pound/8 oz)
  • 28 grams unsweetened chocolate, any brand (1 ounce)
  • 1 1/2 teaspoons instant espresso powder ( you can use up to 2 teaspoons)
  • 200 grams dark brown sugar (1 cup)
  • 5 large eggs (250-270 grams)
  • 300 grams granulated sugar (1 1/2 cups)
  • 1/2 teaspoon salt
  • 1 tablespoon vanilla extract
  • 185 grams King Arthur all-purpose flour (KA for chewier) (1 1/3 cups)
  • 84 grams chocolate chips or chunks (1/2 cup)
  • 2/3 cup walnuts (optional)


  • Preheat the oven to 330 degrees F. You can use regular or convection. In my convection oven they take exactly 25 minutes at the internal temperature hovers around 200 degrees F when they are done.
  • Line a 15x10 inch rimmed sheet pan with a sheet of parchment. Grease the parchment with a little more butter (or use coconut oil).
  • Begin melting the butter in a heavy duty saucepan. When it's halfway melted, add the chocolate and stir well. Turn heat to low and gently melt the chocolate with the butter. This can also be done in a double boiler.
  • When chocolate is melted, remove the hot chocolate from the stove and stir in the espresso powder and dark brown sugar. Stir well to remove any lumps of brown sugar. Set aside to cool.
  • In a mixing bowl, whisk the 5 eggs together. Whisk in the granulated sugar, salt and vanilla. Stir in the melted chocolate mixture.
  • Add the flour and stir until blended. Make sure the batter is completely cool (you don't want to melt the added chocolate chips) and add chocolate chips and nuts.
  • Scrape into the sheet pan and spread evenly. Dot the top with extra chocolate and nuts if desired.
  • Bake for about 25 minutes or until internal temperature hovers around 200 -- a little over is okay. The timing may vary with your oven, so it is helpful to use a meat thermometer the first time. Check them at 20 minutes if possible.
  • Let cool, then chill brownies. Lift from pan and cut into squares.


The texture is much better when completely cooled, chilled and brought back to room temperature.