Pre-heat oven to 350 degrees and line a cupcake tin with papers.
Cream butter and sugar in a stand mixer or in a large bowl with a hand mixer, until light and fluffy.
In a separate bowl, whisk together the flour, baking flour, and salt together.
Slowly mix the dry ingredients into the butter and sugar, alternating with the milk. Add the vanilla and mix until just blended, taking care not to over-mix. The batter will be thick.
In another separate bowl, whisk the egg whites with a hand mixer until stiff peaks form. Gently fold the egg whites into the batter, until just blended. Fold in the strawberries, as well.
Fill cupcake papers about ¾ of the way with batter. Bake for 16-18 minutes, until a toothpick inserted into the center of a cupcake comes out clean.
After cooling in the tin for a few minutes, move cupcakes to wire rack to cool completely.
Core out center of cupcake with a cupcake corer or knife and fill each cupcake with the cooled strawberry filling. If you want, you can place the cored out portion of the cupcake back on.
Pipe frosting on to cupcakes and top each with half a fresh strawberry.