Whisk together the cake flour, baking powder, baking soda, and salt in a medium bowl. Set aside.

Beat the butter and granulated sugar in a stand mixer on medium-high for 3 minutes until pale and fluffy.

Add the egg, egg yolk, sour cream, vanilla extract, and almond extract. Mix on medium until smooth and combined, about 1 minute.

Add the flour mixture and mix on low just until no dry streaks remain. Do not overmix.

Cover the bowl with plastic wrap and refrigerate for at least 30 minutes, or up to overnight.

Heat the oven to 175 C / 350 F. Line two baking sheets with parchment paper.

Scoop the chilled dough into balls using a 2-tablespoon cookie scoop (about 45 g each) and place them 5 cm apart on the prepared sheets.

Press each ball gently with the flat bottom of a glass to about 1.5 cm thick.

Bake for 11 to 13 minutes, until the edges look just set and the centers appear slightly underdone. The tops should stay pale with no browning.

Let cookies cool on the pan for 5 minutes, then transfer to a wire rack and cool completely before frosting.

Beat the butter on medium-high for 2 minutes until smooth and slightly airy.

Add the sifted powdered sugar in two additions, mixing on low between each, then add the vanilla, almond extract, and salt.

Add heavy cream one tablespoon at a time, mixing on medium, until the frosting is thick but spreadable.

Tint with gel food coloring if using, mixing until the color is even.

Spread a generous layer of frosting onto each cooled cookie using an offset spatula or the back of a spoon.

Add sprinkles immediately while the frosting is still wet. Let set for 45 to 60 minutes before stacking or packaging.