Preheat the oven to 350°F. Line a 9×13 baking dish with parchment paper, set aside.

Cut the butter into tablespoons. Place the chocolate chips in a large bowl and add the cut-up butter on top—place in the microwave and microwave for 30 seconds. Stir, microwave for another 30 seconds, and stir again. Continue to microwave in 15-second intervals, stirring in between, until everything is melted and smooth.

Add the sugar to the chocolate mixture and stir to combine. Add the eggs one at a time, mixing them in thoroughly before adding the next. Stir in the vanilla.

Whisk together the flour, cocoa powder, baking powder, and salt in a large bowl.

Pour the wet mixture into the dry ingredients and stir until combined with no dry patches left.

Spread out the mixture into the prepared baking dish. Bake for 50-60 minutes or until a toothpick inserted into the center comes out clean, a few moist crumbs are okay but there should be no wet batter.

Let cool completely.

While the brownies are cooling, make the frosting. Place the butter into the body of a stand mixer with the paddle attachment or in a large bowl with a hand mixer. Whip the butter until smooth.

Add the powdered sugar a little at a time until fully incorporated. Add the salt, pureed strawberries, vanilla, and strawberry extract if using. Stir it in until combined, then whip on medium-high speed for 3 minutes until light and fluffy. Add red food coloring if desired until the color you want is achieved.

Frost the top of the brownies with the strawberry buttercream, cut, and serve.