Preheat oven to 350℉. Spray 8 inch round cake pans with cooking spray and cover the bottom of the pans with parchment paper.
Strawberry reduction. Remove the tops of the strawberries, slice in half and wash. Place the berries in a sauce pan over medium heat. Stirring continuously, let berries cook down about 12-15 minutes. As the berries get soft, use your spoon to mash and break berries into pieces. Turn down the heat if needed to keep the berries from scorching. When the berries have been reduced to about 1 cup, remove sauce pan from the stovetop and let cool. Set aside 4 tablespoons of the strawberry reduction for the buttercream frosting.
Make the cake. Using a stand mixer cream the butter, oil and sugar together until fluffy. Mix in egg whites, sour cream and vanilla until all ingredients are incorporated.
In a separate bowl, whisk together the dry ingredients- flour, cornstarch, baking powder and salt.
Next add the dry ingredients and the evaporated milk into the the wet ingredients by alternately adding ⅓ of the flour mixture, then ½ of the milk, then ⅓ of the flour, the rest of the milk, then the rest of the flour mixture. Mix just until everything is incorporated.
Lastly, mix in the strawberry reduction (minus the 4 tbsps set aside for the frosting), the freeze dried strawberries and 1 drop red gel food coloring. Mix until all of the batter is pink.
Pour strawberry cake batter evenly into the prepared cake pans. Tap the pans lightly on the counter top to remove any air pockets in the batter. Bake until the centers spring back when lightly touched- 25-35 minutes. Remove from ovens and set aside. After 10 minutes, remove cakes from pans and cool on cooling racks or put in freezer to cool- about 30 minutes.
Strawberry Buttercream Frosting
Whip room temperature butter until light and creamy. Add in 2 cups of sugar. Mix in on low speed to keep sugar from dusting up. Add in 2 more cups and mix, then add in sugar 1 cup at a time until you reach 6 cups. Mix in the reserved strawberry reduction, freeze dried strawberries, vanilla extract and pinch of salt. Whip until your buttercream is thick and fluffy. (see notes)
Assemble and frost. Place 1 cake layer on cake plate or pedestal. Add about ⅓ of the frosting to the center of the cake. Using a spatula, work the frosting out to the edges of the cake. Place the 2nd layer on top and press down lightly. Spoon out the rest of the frosting on top of the cake. Using your spatula, work the frosting from the center of the cake over the edges. Then keeping your spatula at a 45° angle against the sides of the cake, turn your plate or pedestal and ice the sides. Work more frosting from the top over the edges as needed. Use your spatula to make swirls on the top of the cake to finish.
Garnish suggestion: Add whole and half berries to one side of the top of the cake. Sprinkle extra chopped pieces of freeze dried strawberries. Add a sprig of mint or two.
Notes
To use all purpose flour, use just 2 cups of flour.When making buttercream, whip room temperature butter until it becomes fluffy before adding the sugar.Making frosting is more about texture than measurement. The strawberry buttercream recipe for this cake calls for 4-6 cups of confectioners, or powdered, sugar, but you could end up adding more. How do you know when to stop? Start by adding 2 cups and mixing and then adding 2 more and so on until you get the consistency of a thick, but soft frosting.If your buttercream becomes too stiff, add 1 tablespoon of room temperature milk to loosen it up. You could also use 1 tablespoon of warm water.Be careful not to over bake the cakes. You want the centers to be soft and spring back when touched. If your cake is dry, it's been baked too long.Want even more strawberry flavor? Add more ground or chopped freeze dried strawberries.Where to find freeze dried strawberries in the grocery store? You should find them on the snack aisle where other fruit snacks, like fruit rollups, dried bananas slices and dried apples are.For max flavor, peak-of-season strawberries work best for this recipe.