Start by preheating your oven to 325℉ (165C/145C Fan) and lining your square baking tray with parchment paper.
In a large mixing bowl, whisk together your sugars and melted butter until well emulsified.
Then add the eggs and vanilla, beating to combine.
Sift the flour, baking powder, cornstarch, salt and cinnamon into the wet ingredients and then stir with a spatula until just combined.
Finally, add the cream cheese morsels or white chocolate chips and stir to combine.
Pour the batter into the prepared baking pan.
In a small bowl stir, together the ingredients for your cinnamon sugar swirl (the brown sugar and cinnamon) and sprinkle generously over the top of your batter.
Using a kitchen knife, swirl this lightly into the batter.
Bake in the preheated oven for about 40-50 minutes, until a toothpick inserted in the centre comes out mostly clean.
Once baked, remove and allow to cool in the pan for about 2 hours, to allow the blondies to set.
In a small bowl, stir together the powdered sugar, cream cheese and vanilla until you have a thick smooth glaze. Then pipe over the blondies before slicing and serving.