Black And White Cookies With Orange Marmalade - cake flour

Ingredients

• 2 1/2 cups cake flour or homemade cake flour - see I Say Nomato for instructions
• 1 teaspoon baking soda
• 1 teaspoon salt
• 2/3 cup buttermilk well-shaken
• 1/2 teaspoon vanilla
• 1 teaspoon lemon juice
• 2/3 cup unsalted butter softened
• 1 cup granulated sugar
• 2 large eggs
• 1 cup orange marmalade
• 2 cups powdered sugar
• 1 teaspoon light corn syrup
• 1 teaspoon vanilla extract
• 2 tablespoons hot water
• 4 ounces semi sweet chocolate
• 3 tablespoons butter
• 1 tablespoon light corn syrup