Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking pan or line it with parchment paper.

In a medium saucepan, melt the butter and chopped chocolate over low heat, stirring until smooth. Remove from heat and let it cool slightly.

In a large mixing bowl, combine the granulated sugar, brown sugar, eggs, and vanilla extract. Whisk until well blended.

Slowly pour the melted chocolate mixture into the sugar and egg mixture, stirring continuously until fully combined.

Add the flour and salt to the mixture, stirring just until incorporated. Do not overmix.

Gently fold in the sliced strawberries and chocolate chips, if using.

Pour the brownie batter into the prepared baking pan, spreading it evenly.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.

Allow the brownies to cool in the pan for at least 15 minutes before slicing into squares.