Step 1

Preheat the oven to 350F (180C or 160C on a forced fan oven) degrees and line a 12-cavity muffin pin with cupcake papers. I typically get 12-14 cupcakes.

Step 2

In a medium sized bowl, whisk together the cake flour, baking powder, baking soda and salt. Set aside.

Step 3

Using an electric mixer cream together the butter and sugar on medium speed until light and fluffy (about 2-3 minutes). Continue beating and add in the egg whites and vanilla (another 30 seconds).

Step 4

Turn off the mixer, scrape down the sides of the bowl and stir in the yogurt.

Step 5

Sift in the flour mixture, then mix on low speed until almost combined. Drizzle in the milk and continue beating until combined. Stop mixing as soon as everything is incorporated.

Step 6

Spoon the batter evenly into the lined muffin tin filling each about two thirds of the way full. You should end up with 12-14 cupcakes.

Step 7

Bake for 15-18 minutes until an inserted toothpick comes out clean. Leave to cool in the pan for about 10 minutes then remove the cupcakes and continue cooling on a wire rack.

Step 8

Haul the strawberries to remove the centers.

Step 9

Process the strawberries in a blender or food processor until no lumps remain.

Step 10

Pour the sauce through a wire sifter to remove the seeds. Do this a little at a time, using a metal spoon to push the puree through the sifter.

Step 11

Transfer the puree to a small saucepan over medium heat. Bring the mixture to a gentle boil while stirring.

Step 12

Allow the sauce to boil for about 15-30 minutes (while occasionally stirring) and reduce to about 1/3 to 1/4 of the original volume. It should look thick like jam. Remove from the heat and cool until it reaches room temperature. You can speed this up in the fridge if needed.

Step 13

In a large bowl, beat the butter on medium speed until fluffy. Slowly add about 2 cups of the powdered sugar and continue beating until combined.

Step 14

Beat in the salt and 3-4 tablespoons of the cooled strawberry sauce. Make sure your strawberry sauce is cold before adding it to the buttercream.

Step 15

Beat in the rest of the powdered sugar about 1/2 cup at a time until the desired sweetness & thickness is reached. If the icing seems too thick, add in a tablespoon of whipping cream.

Step 16

Frost the cupcakes using a piping bag or by spreading the icing with an icing spatula. I used a piping bag with a 1M tip.