Preheat your oven to 350°F. Grease and line an 8x8 inch baking pan with parchment paper.
In a microwave-safe bowl, melt the butter and the 2 ounces of chocolate together. Stir until smooth.
1/2 cup butter, 2 ounces semi-sweet or bittersweet chocolate
Stir in the granulated sugar until well combined then add in the eggs one at a time then mix in the vanilla extract.
1 cup granulated sugar, 2 large eggs, 1 teaspoon vanilla extract
In a separate bowl, sift together the cocoa powder, all-purpose flour, and salt.
1/3 cup unsweetened cocoa powder, 1/2 cup all-purpose flour, 1/4 teaspoon salt
Add the dry ingredients to the wet ingredients, mixing until just combined. Fold in 1 cup of the chocolate chunks.
1 & 1/2 cup semi sweet chocolate chunks
Pour the batter into the prepared baking pan and spread it evenly and top with the 1/2 cup leftover chocolate chunks.
Bake in the preheated oven for about 25-28 minutes or until a toothpick inserted into the center comes out with a few moist crumbs.
Allow the brownies to cool in the pan before cutting them into squares.
Notes
Pan conversions:
8x8 as written, 9 thick squares.
For a 9x9, increase all ingredients by 25% and start checking at 25 minutes.
For a 9x13, double everything and check at 28 to 30 minutes.
Doneness: the toothpick should come out with moist crumbs, never clean. A clean toothpick means overbaked. Wet batter on the toothpick means give it 3 more minutes. If your brownies baked thin, the pan was wider than 8x8. Adding time will not fix thin, it only dries the edges.