Melt the butter and chocolate

• Combine the butter and semi-sweet chocolate in a saucepan.
• Melt over low heat, stirring until smooth.

Whisk the sugars and eggs

• Add the granulated sugar and brown sugar.
• Add the eggs and vanilla extract.
• Whisk until the mixture is glossy and well combined.

Fold in the dry ingredients

• Sift in the cocoa powder, salt and flour.
• Fold gently until just combined, then stir in the chocolate chunks.

Bake the brownies

• Pour the batter into a lined baking dish and spread evenly.
• Bake at 350 °F (175 °C) until the top is crinkled and a toothpick comes out with moist crumbs.

Cool and cut

• Let the brownies cool completely in the dish.
• Cut into squares and serve.