Step 1

Preheat the oven to 350°F. Line baking sheets with parchment paper.

Step 2

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

Step 3

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugar on medium-high speed until light and fluffy, about 3 minutes. Scrape down the sides and bottom of the bowl with a rubber spatula. On low speed, add the egg, sour cream, vanilla, and almond extract (if using). Turn the speed to medium and beat until the mixture is thicker (will look slightly curdled), about 2 minutes. Scrape down the bowl again. On low speed, gradually add the flour mixture, beating until just combined.

Step 4

Using a medium spring-loaded scoop (1 ½ tablespoons), drop balls of cookie dough onto prepared sheets in four rows of three. Roll each ball until smooth, then flatten them to ¼-inch thick with the palm of your hand. If the dough is too sticky, dampen your hands slightly as needed.

Step 5

Bake until the cookies appear dry on the top but still pale at the edges, about 11 minutes.

Step 6

Place on a wire rack to cool completely.

Step 7

In the bowl of a stand mixer fitted with the paddle attachment, add the sugar and butter. Mix on low speed until smooth and then increase the speed to medium and beat for another 3 minutes.

Step 8

Add the salt, vanilla, and cream and beat on medium speed for 1 minute, adding more cream if needed. Add the food color, if using.

Step 9

Frost each cookie with a heaping tablespoon of frosting. Use the back of a spoon or an offset spatula to spread it evenly. If you’d like to add sprinkles, do so right after frosting each cookie, as the frosting can set quickly. Allow the cookies to sit for about 4 hours or until the frosting is firm. This time may vary depending on your kitchen’s humidity.

Step 10

Store at room temperature in an airtight container for up to six days or up to six weeks in the freezer. Thaw in fridge overnight, then let come to room temperature before serving. Note that coloring of sprinkles may bleed when frozen and thawed.