Heat the oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment paper, leaving about 2 inches of overhang on the two long sides so you can lift the slab out later.
In a large bowl, whisk the melted butter and brown sugar together until smooth and glossy, about 1 minute. Whisk in the eggs one at a time, then the orange zest and vanilla, until fully combined.
In a medium bowl, whisk the flour, baking powder, ground ginger, and salt. Add the dry ingredients to the wet and stir with a spatula just until no streaks of flour remain — do not overmix or the bars turn tough.
Fold in the chopped dried cranberries and white chocolate chips, distributing them evenly through the thick batter.
Spread the batter into the prepared pan in an even layer, pushing it into the corners with the spatula. Bake for 22–25 minutes, until the edges are set and golden and a toothpick inserted into the center comes out with a few moist crumbs.
Cool completely in the pan on a wire rack, at least 1 hour. Do not frost a warm slab — the frosting will slide right off.
Beat the softened cream cheese and butter in a medium bowl on medium speed until smooth and fluffy, about 2 minutes. Add the powdered sugar, vanilla, and orange zest and beat on low until combined, then on medium until light and spreadable, about 1 minute. Add the orange juice only if the frosting feels too stiff.
Spread the frosting evenly over the cooled blondie, all the way to the edges. Sprinkle the finely chopped cranberries over the top, then drizzle with the melted white chocolate in thin zigzags.
Refrigerate for at least 20–30 minutes to set the frosting. Lift the slab out by the parchment overhang and cut into 12 squares, then cut each square diagonally into 2 triangles for the classic cafe look. Serve chilled or at cool room temperature.