Preheat oven to 350 F. In a medium sized mixing bowl, whisk to combine the flour, baking powder, baking soda, cinnamon, salt and cocoa powder. Set aside.
In a large mixing bowl, add the brown sugar, granulated and orange zest. Use your fingertips to rub the zest into the sugars. (Instead of your fingers, use mixer to combine). This helps to bring out the orange flavor.
Beat the butter and sugars with an electric mixer on medium speed til light and fluffy, about 2 minutes.
Beat in the vanilla, egg, and egg yolk one at a time until incorporated.
Add the dry ingredients and mix until just combined. Mix in most of the chopped chocolate til just combined. Leave a little extra chocolate out so that you can top the cookies with it.
Pour 1/4 cup granulated sugar to a shallow bowl. Add 2-3 teaspoons of orange zest (optional) and rub it into the sugar with your fingertips.
Scoop dough using a cookie scoop or a tablespoon. Roll cookie dough balls in granulated sugar until coated.
Place cookie dough balls about 2 inches apart. Press a couple of extra pieces of chopped chocolate into the dough balls. Lightly press the dough balls down with your fingertips. Bake 7-9 minutes.
Leave cookies on baking sheet for 5 minutes then transfer cookies to a wire rack to cool completely
Once cookies have cooled completely, melt the white chocolate. Chop the chocolate and place it in a heat proof bowl. Microwave in twenty second bursts, stirring well in between each burst til chocolate has melted.
Drizzle the chocolate over the cookies or dunk/dredge half the cookies or the top of the cookies in the melted chocolate.
Zest extra orange over the cookies while the white chocolate is still wet, if desired. Set cookies on the cookie rack to allow white chocolate to set.