Preheat oven to 325 degrees. Butter an 8 x 8 baking dish and set aside.
In medium bowl whisk together flour, baking soda, and salt. Set aside.
In large mixing bowl cream butter until smooth and light in color. 2 minutes. Add in sugars and beat another 2 minutes until fluffy.
Beat in egg and both extracts for 1 minute. Add in sour cream & beat for 1 additional minute.
Add flour mixture in and fold together until just combined and a dough forms. Place 1/2 of the dough into a separate bowl.
Add cocoa powder to 1/2 of the dough and mix until just combined. (I like to use my hands to really get a good mix on it.)
Place the chocolate dough into prepared baking dish and press into an even layer.
Dollop the vanilla dough on top of the chocolate layer and press evenly.
Bake in preheated oven for 35-40 minutes until golden brown and a toothpick inserted into middle comes out clean. Place on a wire rack and cool slightly. Pull cookie bars out and let cool completely on the wire rack.
In the meantime, puree strawberries and strain through a strainer. Measure out 1/2 cup juice. Start combining 1-2 cups of powdered sugar into the juice until smooth and a thick consistency.
Pour over cooled cookie bars and spread to the edges. Add sprinkles if desired. Cut into bars and enjoy these tasty treats.