Preheat the oven to 350°F. Line a 10x15x1 (this will also work with a 9x13 pan, cook times may vary) pan with parchment paper, set aside. In a medium-sized bowl, stir together the flour, baking powder, ginger, and salt, set aside.
In a large bowl, whisk together the melted butter, brown sugar, and granulated sugar until combined.
Whisk in the eggs until fully incorporated.
Add the orange zest and vanilla, whisk to combine.
Add the dry ingredients to the bowl and stir it in until there are no dry patches left.
Add the chopped cranberries and chocolate chips, fold them in.
Spread this mixture into the prepared baking pan and smooth it out. Bake for 18-22 minutes until golden brown and a toothpick inserted into the center comes out clean.
Place on a wire rack to cool completely.
While the bars cool, make the frosting by adding the cream cheese to a medium-sized bowl and mix it with an electric hand mixer until smooth. Add in the powdered sugar a little at a time until mixed in. Add the orange zest and vanilla, mix it in. Add half of the melted white chocolate and mix it in.
Once the bars are cool, take them out of the pan and smooth the frosting over the top.
Sprinkle the chopped cranberries on top. Drizzle the remaining melted white chocolate on top, in an overlapping zig-zag pattern.
You can cut and serve the bars immediately or place them in the refrigerator so the frosting can set slightly if you want a firmer bar.