In the work bowl of a food processor, pulse fresh strawberries until almost smooth. (You should have about 1 cup or 205 grams.) Transfer to a small saucepan; bring to a boil over medium heat. Reduce heat to medium-low, and cook, stirring frequently, until mixture is a thick, concentrated paste and reduced to ¼ cup (70 grams), 15 to 20 minutes. Remove from heat, and let cool completely.
Preheat oven to 350°F (180°C). Line a 12-cup muffin pan with foil liners.
In the bowl of a stand mixer fitted with the paddle attachment, beat butter and granulated sugar at medium speed until light and fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add eggs, one at a time, beating until combined after each addition. Beat in vanilla.
In a medium bowl, whisk together flour, freeze-dried strawberries, baking powder, and salt. In another medium bowl, whisk together cooled strawberry purée, milk, and yogurt. With mixer on low speed, gradually add flour mixture to butter mixture alternately with strawberry mixture, beginning and ending with flour mixture, beating until just combined after each addition. Divide batter among prepared muffin cups (about a heaping ¼ cup or 65 grams each).
Bake until an instant-read thermometer inserted in center registers 200°F (93°C) to 210°F (99°C), about 25 minutes. Let cool in pan for 5 minutes. Remove from pan, and let cool completely on a wire rack.
Spoon Vanilla American Buttercream into a pastry bag fitted with a medium open star piping tip (Ateco #826). Pipe buttercream onto cooled cupcakes as desired. Garnish with sparkling sugar and sprinkles, if desired. Refrigerate in an airtight container for up to 3 days.