1-Preheat and Prepare: First, preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners. This step helps the cupcakes bake evenly and prevents sticking, making cleanup easy.

2-Mixing the Batter: In a mixing bowl, cream together the softened unsalted butter and granulated sugar until light and fluffy. Then, add the large egg plus 2 egg whites one at a time, followed by the pure vanilla extract for that extra flavor boost.

3-Combining Dry and Wet Ingredients: Sift the cake flour, baking powder, and salt in a separate bowl to keep things airy. Gradually mix the dry ingredients into the wet mixture, alternating with the full-fat sour cream and whole milk. Gently fold in the chopped strawberries to maintain that moist texture.

4-Baking and Cooling: Spoon the batter into the liners, filling them about two-thirds full. Bake for 18-22 minutes, or until a toothpick comes out clean. Let the cupcakes cool completely before adding the strawberry buttercream frosting for the best finish.