In a medium bowl, sift 5 cups of the flour, the baking soda, baking powder, salt, and cocoa powder.

In the bowl of a stand mixer beat the butter and granulated sugar at medium speed until light and fluffy, about 3 minutes. Add the eggs, one at a time, until incorporated. Add the vanilla and sour cream and beat on low speed until combined. Gradually add the flour mixture and beat until just combined. The dough should be pliable consistency for rolling, so add additional flour, about 1/4 cup at a time, until pliable (up to 1 cup more flour). Divide the dough into two sections and flatten each into disks. Wrap with plastic wrap and chill in the refrigerator for 6 to 8 hours or overnight.

Preheat the oven to 425°F. Line large baking sheets with parchment paper or nonstick baking mats.

Dust a work surface and rolling pin with a mixture of flour and cocoa powder. Roll the dough out to 1/4-inch thickness. Using a 2 1/2-inch round cookie cutter, cut out circles and transfer to a baking sheet.

Bake for 7-8 minutes. Immediately transfer the cookies to a wire rack to cool.

In the bowl of a stand mixer, beat the butter and vanilla. In a medium bowl sift together the powdered sugar and cocoa powder. Gradually beat in the sugar mixture until well incorporated and smooth. Add in heavy cream, 1 tablespoon at a time, until desired consistency.

Once the cookies have cooled completely, frost and add sprinkles. Place the cookies in an airtight container at room temperature overnight before serving to allow the flavors to develop.