Black and White Cookies

Ingredients

• 1 ⅓ cups all-purpose flour (160g)
• ½ tsp baking soda
• ½ tsp salt
• 6 Tbsp unsalted butter (room temperature, 85g)
• ½ cup granulated sugar (100g)
• 1 large egg (room temperature)
• 2 tsp vanilla extract (10mL)
• ⅓ cup buttermilk (80mL)
• 2 cups confectioners’ sugar (240g)
• 2 tsp lemon juice (fresh optional)
• 2 Tbsp water plus more as needed
• 1 Tbsp light corn syrup
• ½ tsp vanilla extract
• 3 Tbsp cocoa powder (dutch-process preferred, 18g)