Butter a 9- by 13-inch baking pan and line with parchment paper, leaving extra paper extending up the two long sides of the pan – this will function as handles to help you lift the brownies out of the pan later. Butter the parchment paper.

Preheat the oven to 325 degrees F.

Combine the butter and bittersweet chocolate in a microwave-safe bowl and microwave, in short increments and stirring frequently, until the butter and chocolate are completely melted and smooth. Cool slightly.

In a large bowl, combine the light brown sugar, granulated sugar, eggs, salt, and vanilla extract and whisk to combine. Stir in the melted butter-chocolate mixture, then add the flour  and chocolate morsels, stirring just until combined.

Pour the batter into the prepared pan, and sprinkle the nuts evenly over the top.

Bake for 35 to 40 minutes, or until shiny on top and nearly cooked through. Don’t overcook – these are supposed to be fudgy.

Remove from the oven and set aside on a wire rack until thoroughly cooled, up to several hours. The longer you let these cool, the easier it will be to cut into neat squares.

Lift the brownies out of the pan by grasping the two long edges of parchment and transfer to a cutting board. Cut the brownies into small squares and serve, or place in an airtight container for up to several days.

Makes about 24 two-inch brownies.