Preheat oven to 350°F and line 2-3 baking sheets with parchment paper.

In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, beat the softened butter and granulated sugar on medium speed until light and fluffy, about 1-2 minutes.

Add the egg and vanilla extract, and beat on medium-low speed until combined, about 30 seconds.

Gradually add the dry ingredients to the butter mixture in two parts, mixing on low speed until just combined.

Gently fold in the Christmas jimmies sprinkles using a spatula until evenly distributed.

Use a 3-tablespoon cookie scoop to portion the dough (about 48-50 g each).

Roll each scoop into a ball and place them on the prepared baking sheets about 2 inches apart.

Slightly flatten each dough ball with your fingers or the bottom of a glass, keeping the cookies at least ½ inch thick.

Bake for 9-11 minutes, or until the edges are set and the tops look soft and no longer glossy.

Remove from oven and immediately shape into a perfect circle by gently rotating a cookie cutter or glass around each cookie.

Cool the cookies on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely.

In the bowl of a stand mixer fitted with the whisk attachment, beat the cream cheese and butter on low speed until smooth, creamy, and lump-free, about 1-2 minutes.

Add the vanilla extract and salt, then beat until just combined.

Add the sifted powdered sugar in three parts, beating until just combined each time.

Gradually drizzle in the cold heavy cream while whisking on low speed until stiff peaks form, about 1-1½ minutes.

Pipe the frosting on the cookies or spread it with a spatula to create decorative swirls. Before serving, sprinkle with Christmas sprinkles.