Dissolve baking soda in vinegar. Sift 2 cups flour with 1 teaspoon each of cinnamon, ground cloves, and ground ginger, and a pinch of sea salt.
Mix 3/4 cup molasses, 1 cup packed brown sugar, 2 eggs, 1/2 cup butter, and dissolved baking soda together in a large mixing bowl.
Stir in flour and spice mixture. Add more flour 1/4 cup at a time until the dough is pretty stiff—1/2 to 3/4 cup more total.
Divide the dough in half. Roll out one half at a time on a lightly floured surface to 1/4" thickness. Stamp with a cookie-cutter into 2" rounds. If the dough is sticky, use a pastry knife to lift cookies from the counter.
Bake at 375°F for 8-10 minutes on a parchment-lined cookie sheet until cookies are set and just beginning to brown at the edges. Cool on a wire rack.
Once cookies are cooled, melt white chocolate in a double boiler until smooth. Spread melted chocolate on top of each cookie in a thin layer with the back of a spoon. Set on a wax paper-lined tray and allow to cool completely until chocolate is set.
Yields 4 1/2 dozen 2-inch cookies.
I find that brown sugar helps to keep the cookies soft, but white sugar can also be used.
Adding vinegar to baking soda is an old fashioned way of activating the baking soda if they didn't have baking powder. We still use the method to preserve the tradition.
Due to the dark color it can be difficult to know if the cookie is done. It is best to test one or two at 8 or 9 minutes rather than over-baking so the cookies remain chewy.