Steps
1. Preheat the oven to 350°F (175°C) and grease a baking dish.
2. In a microwave-safe bowl, melt the butter and chocolate together, stirring until smooth.
3. In a separate large mixing bowl, beat the sugar, eggs, and vanilla extract until well combined.
4. Gradually add the melted chocolate mixture to the sugar and eggs, mixing well.
5. Sift in the flour, cocoa powder, and salt, and stir until just combined.
6. Fold in the chocolate chips (and optional nuts) into the batter.
7. Pour the batter into the prepared baking dish and smooth the top.
8. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs.
9. Allow the brownies to cool before cutting into squares and serving.