Mini Black-and-White Cookies

Preheat oven to 350 degrees and put racks in upper and lower thirds of oven

Butter 2 large baking sheets

Whisk together flour, baking soda and salt

Stir buttermilk and vanilla in a separate cup

Beat butter and sugar until pale and fluffy (about 3 minutes)

Add egg, beating until well combined

At low speed, add flour mixture and buttermilk mixture alternately in batches beginning and ending with flour mixture and mix just until smooth

Drop round teaspoons of batter 1” apart onto baking sheets

Bake switching positions of sheets halfway through baking, until tops are puffed and edges are pale gold and cookies spring back when touched (6-8 minutes total)

Transfer to a rack to cool

Stir together confectioner’s sugar, corn syrup, lemon juice and 2 Tbsp. water in a small blow until smooth

Add water if icing is not easily spreadable (1/2 tsp. at a time)

Transfer 1/2 of icing into another bowl and add cocoa, adding more water (1/2 tsp. at a time) to thin to same consistency as vanilla icing

Cover surface with a dampened paper towel, then cover bowl with plastic wrap

Spread white icing, with offset spatula, on 1/2 of flat side of each cookie first and spread chocolate icing over other half

Once icing is dry, keep cookies layered between sheets of wax paper in an airtight container at room temp 4 days