Preheat the oven to 350°F and line two baking sheets with parchment paper.
In a stand mixer, combine butter, sugar, baking powder, and salt. Mix on low speed with the paddle attachment, then increase to medium and beat until creamy (about 5 minutes).
In a separate bowl, whisk together egg whites, cream, and vanilla. Gradually add this mixture to the butter mixture in 4-5 increments, mixing until smooth each time.
Gradually sprinkle in the cake flour, mixing on low speed until a soft dough forms. Fold the dough once or twice to ensure even mixing.
Transfer the dough to a piping bag fitted with a ½-inch plain tip.
Pipe 1 ¼-ounce portions onto the baking sheets, leaving 2 ½ inches of space between cookies.
Bake for approximately 15 minutes, until puffed and pale gold around the edges. Let cool completely before frosting.