Preheat oven to 350°F and line baking sheets with parchment.
Mix dry ingredients; beat butter and sugar until fluffy. Add egg and vanilla, then combine dry ingredients. Fold in sprinkles.
Portion dough with a cookie scoop, shape into balls, flatten slightly, and bake for 9-11 minutes. Cool and shape into circles.
Make frosting by beating cream cheese and butter, then add vanilla, salt, powdered sugar, and heavy cream until stiff peaks form. Pipe or spread over cookies and decorate with sprinkles.
Notes
Ensure frosting is not overwhipped to prevent splitting. Use cold heavy cream for best frosting consistency.