Preheat oven to 350 degrees
Line two baking sheets with parchment paper or silicone baking mats
In a medium bowl, whisk together flour, baking powder, and salt; set aside
Using an electric mixer, beat the butter and sugar on medium-high
speed until pale and fluffy, about 3 minutes
Add the egg white, heavy cream, and vanilla, and beat until combined
Reduce speed to low and add flour mixture in three additions, mixing
until incorporated, scraping down the bowl as needed
Working with 1 heaping tablespoon of dough at a time, roll into balls
and space 2 inches a part on the prepared baking sheets
Using your hands, press down the tops of the balls slightly
Bake until the cookies are just beginning to brown around the edges, 8
to 10 minutes, rotating the sheet halfway through baking
Let the cookies cool completely on the baking sheet