- Preheat the oven to 350°F (175°C). Grease a 9x13 inch baking pan or line it with parchment paper. 
- In a medium saucepan over low heat, melt the butter and chopped chocolate together, stirring until smooth. Remove from heat and let it cool slightly. 
- In a large mixing bowl, combine the granulated sugar, brown sugar, and eggs. Whisk until well combined. Stir in the melted chocolate mixture and vanilla extract. 
- Add the flour and salt to the chocolate mixture, stirring until just combined. Be careful not to 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 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. For best flavor, chill in the refrigerator for an hour before serving.