Preheat your oven to 350°F. Line 2-3 baking sheets with parchment paper.

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

In a stand mixer bowl fitted with the paddle attachment (or using a hand mixer), beat the softened butter and granulated sugar on medium speed until light and fluffy for 1-2 minutes. Scrape down the bowl once or twice.

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

Gradually mix in the dry ingredients in two parts on low speed until just combined. Avoid overmixing.

Carefully fold in the Christmas jimmies sprinkles with a spatula.

Use a 3-tablespoon cookie scoop (about 48-50 g each) to portion the dough. Roll into balls and place 2 inches apart on the baking sheets.

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

Bake for 9-11 minutes, until the edges are set, and the tops look soft and not glossy. Do not let them brown.

After baking, shape the cookies into perfect circles using a larger cookie cutter or glass while they are hot.

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

For the frosting, beat the cream cheese and butter in a stand mixer fitted with the whisk attachment (or using a hand mixer) on low speed until smooth and creamy, about 1-2 minutes. Scrape down the sides as needed.

Add the vanilla extract and salt and beat until just combined on low speed.

Gradually add the sifted powdered sugar in three parts, mixing on low speed for about 10-15 seconds for each addition. Scrape the bowl when needed.

Drizzle in the cold heavy cream (by the tablespoon) while whisking on low speed until stiff peaks form, about 1-1½ minutes. Avoid overwhipping.

Pipe the frosting in a spiral over the cookies, or spread it with a spatula for swirls.

Right before serving, sprinkle some Christmas decorations over the frosting.