Strawberry Filling

1. Combine all the ingredients in a small saucepan over medium heat. Stir to combine and cook until it begins to bubble. Allow to cook 1 minute, then remove from the heat.
2. Transfer to a heat-safe bowl to cool.

Strawberry Cupcakes

1. Preheat oven to 350°F/177°C. Line a muffin pan with cupcake liners. Set aside.
2. In a medium bowl, sift the flour, baking powder, baking soda, and salt. Set aside.
3. In a large bowl, using a hand-held mixer or stand mixer fitted with the paddle attachment, beat the butter and sugar on medium-high speed until smooth and creamy, 2-3 minutes. Scrape down the sides of the bowl as needed.
4. Beat in the egg whites, one at a time, until combined. Scrape down the sides of the bowl and beat in vanilla until mixed well.
5. With the mixer on low speed and in three parts, alternately add the dry ingredients and the milk to the batter, beginning and ending with the dry ingredients. Beat until just combined. Fold in the strawberry puree.
6. Fill cupcake liners 2/3 full and bake for 17-19 minutes, or until a toothpick inserted in the center comes out clean.
7. Allow cupcakes to cool completely in the pans set on a wire rack before filling and frosting.

Strawberry Cream Cheese Frosting

1. In a large bowl, using a hand-held mixer or stand mixer fitted with the paddle attachment, beat the cream cheese and butter together on medium-high speed until smooth and creamy, 2-3 minutes.
2. Add the powdered sugar and mix on low speed until completely incorporated.  Add the strawberry puree and vanilla and combine. Increase to medium-high speed and beat for 2 minutes.

Assemble Cupcakes

1. Using a paring knife or corer, hollow out the centers of the cupcakes without cutting through the bottoms.
2. Spoon or pipe the filling into each cupcake filling to the top of the cupcake.
3. Using a piping bag fitted with a large star tip or an offset spatula, frost the cupcakes to completely cover the filling.