Preheat oven to 350. Line a 7x10 or 8x8 pan with foil and spray with nonstick cooking spray. Set aside.
In a large bowl, whisk together melted butter and cocoa powder until smooth. Add sugar and whisk until blended. Whisk in eggs, one at a time, then whisk in vanilla and flour just until no flour streaks remain in batter. Spread evenly in prepared pan and bake for about 20 minutes or until brownies are puffy and a knife inserted in the center comes out clean. Remove brownies from oven and let cool completely before frosting.
3. Prepare buttercream frosting: In the bowl of your mixer, beat butter and pureed strawberries until blended. Mixture may look a little curdled -- this is okay, it will develop once powdered sugar is added. With the mixer on low, slowly add the powdered sugar, mixing on low until just blended. Increase mixer speed to high and beat for one minute. Frosting should be smooth and fluffy. Spread frosting evenly over prepared brownies and chill for about 30 minutes or longer. Note If you do not have a power mixer, blend butter and puree strawberry together. Mixture may be melted somewhat in microwave for about a minute (enough to allow butter and puree to combine). Using a wooden spoon, slowly add in powdered sugar until all is incorporated. Whip really fast until desired consistency.
4. Prepare chocolate ganache: In a small microwave safe bowl, combine chocolate chips and heavy cream. Microwave for about two minutes, stopping every 30 seconds to stir. Repeat process until melted and smooth and well combined. Stir in corn syrup and let ganache sit for a bit until it's cooled and thickened. Pour ganache over chilled brownies and let brownies chill several more hours until firm. Cut and serve.