Preheat the oven to 325ºF. Line muffin pans with cupcake liners (you'll need about 36) and set them aside.
In a large mixing bowl whisk the dry ingredients together: cake mix, all-purpose flour, granulated sugar, and salt.
Slowly, add in water, sour cream, egg whites, vegetable oil, and vanilla extract. Mix until everything has been combined.
Add batter into the lined cupcake pan, filling 2/3 full.
Bake in preheated oven for 22 minutes or until a toothpick inserted in the center comes out clean or the center bounces back when you touch it.
Remove from the oven and allow the cupcakes to cool on a wire rack.
Make the filling:
In a medium bowl mix together chopped strawberries, strawberry jam, and honey.
Cut out the center of the cupcakes and spoon strawberry filling into the center. Add top back to the cupcake to hold filling in.
Make the frosting:
With an electric hand mixer or a stand mixer (with the paddle attachment), mix butter and shortening until smooth, about 3 minutes. Scrape the sides of the bowl as needed.
Add in milk and vanilla extract.
Slowly, add in confectioners' sugar a little at a time. If frosting is too thick you can add 1 teaspoon of milk until you have reached the texture, you are looking for. Mix frosting for another 3 minutes using the whisk attachment.
Add frosting to a piping bag with a large tip (Wilton 1M or 2D) and pipe frosting on top of the cupcakes. Layer with sliced strawberries to decorate.
Store in an airtight container in the fridge. These are best served the same day so that they don't get too moist in the center.
Because of the fruit filling, these are not the best for freezing.
Refer to the article above for more tips and tricks.The calories shown are based on the recipe making 36 cupcakes, with 1 serving being 1 cupcake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information. The information in the nutrition box are calculated through a program and there is room for error. If you need an accurate count, I recommend running the ingredients through your favorite nutrition calculator.**