Preheat your oven to 350°F (175°C) and prepare a 9x13 inch baking dish by greasing it or lining it with parchment paper for easier removal.

In a medium saucepan over low heat, melt the butter, then remove it from the heat and stir in the sugar, eggs, and vanilla extract until well combined.

In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt to combine thoroughly.

Gradually fold the dry mixture into the wet mixture until just combined. Be careful not to overmix, as this can lead to dense brownies.

Gently fold in the chopped strawberries and, if using, the chocolate chips, until they are evenly distributed.

Pour the batter into the prepared baking dish, spreading it out evenly, and bake in the preheated oven for about 25-30 minutes, or until a toothpick inserted comes out with a few moist crumbs.

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