Preheat the oven to 350°F (180°C) and line a 12-cup cupcake pan with paper liners.

In a bowl, whisk together cake flour, salt, baking powder, and baking soda, and set aside.

In a measuring jug, combine strawberry puree and sour cream until well blended and set aside.

In a large bowl (or the bowl of a stand mixer) blend sugar, butter, and oil for one minute.

Add egg and yolks one at a time and blend for another minute.

Blend in vanilla and food coloring.

Add the dry ingredients in three additions, alternating with the puree mixture. Blend until just combined and uniform, scraping down the sides of the bowl once or twice.

Divide batter evenly among the 12 cupcake liners and bake for 20-25 minutes, or until a thin knife inserted into the center comes out clean.

Let cool in the pan for 10 minutes before removing from the pan. Cool completely before frosting.

In the microwave or on the stove, bring the strawberry puree to a boil and reduce in half, to ¼ cup (2floz/57ml). Let cool completely before proceeding. (Note: If you are doing this in the microwave, use a large bowl.)

Cream butter and powdered sugar until well combined.

Add cream cheese and blend until incorporated and fluffy.

Mix in the cooled strawberry puree and strawberry extract. If a deeper pink color is desired, add in a drop of food coloring.

Once the cupcakes are cool, pipe or spread the frosting onto the cupcakes and decorate with sprinkles. Store in an airtight container in the refrigerator for up to two days or freeze for up to a month. If frozen, defrost on your counter at room temperature for two hours.