1-Melt the 1/2 cup unsalted butter and two 4-ounce semi-sweet chocolate bars together using a microwave or stovetop, then let it cool for 5 minutes.

2-Preheat your oven to 350°F (177°C) and line a 9-inch square baking pan with parchment paper for easy removal.

3-Whisk the 3/4 cup granulated sugar and 1/4 cup packed brown sugar into the cooled chocolate mixture until well combined.

4-Whisk in the 3 large eggs one at a time, followed by 1 teaspoon pure vanilla extract, to create a smooth batter.

5-Whisk in the 2/3 cup all-purpose flour, 2 tablespoons unsweetened cocoa powder, and 1/4 teaspoon salt until just smooth, then fold in the 1 cup semi-sweet chocolate chips. The batter should be semi-thick.

6-Spread the batter evenly in the prepared pan and bake for 32-35 minutes, checking at 30 minutes with a toothpick for a few moist crumbs.

7-Cool the brownies in the pan on a wire rack for 1-2 hours, then lift them out using the parchment paper.

8-For the frosting, beat the 1/2 cup unsalted butter until creamy, then add 1 and 1/2 cups confectioners’ sugar, 1/3 cup unsweetened cocoa powder, 3 tablespoons warm heavy cream or milk, 1/2 teaspoon pure vanilla extract, and a pinch of salt. Mix on low for 30 seconds, then on high for 1 minute, adjusting salt as needed.

9-Spread the frosting over the mostly cooled brownies and cut into squares with a sharp knife, wiping the knife after each cut.