Place thawed strawberries and water in food processor or other blender and blend until smooth.
Heat on stove at a medium high simmer for 10-20 minutes until reduced by half; set aside in the fridge to cool. Once cooled, separate into a 25/75 ratio. It should come out to roughly 2 cups. (So for 2 cups of strawberry reduction separate ½ cup from the other 1 ½ cups.)
Be sure to cool strawberry reduction COMPLETELY.
Preheat oven to 350 degrees Fahrenheit.
Prepare the cake batter base by combining the flour, sugar, baking powder, baking soda, and salt until evenly combined.
Add to that the softened sticks of butter, oil, egg whites, vanillaand sour cream and mix until evenly combined (batter will be thick.)
Fold in 75% (about a 1 ½ cups) of the strawberry puree reduction.
Fill lined muffin tin and bake for 24-32 minutes until toothpick inserted into center comes out clean. Let cool.
Cream together the butter and powdered sugar for the frosting and beat until smooth. Beat in the remaining 25% of the cooled strawberry puree reduction (about ½ cup)
Pipe or spread onto cooled cupcakes.
Top with a fresh strawberry (optional).