Preheat the oven to 350°F (175°C) and lightly grease an 8-inch cast iron skillet with butter.
In a medium bowl, combine the flour, brown sugar, cinnamon, and salt for the streusel. Cut in the cold butter using your fingertips or a pastry cutter until coarse crumbs form. Refrigerate until ready to use.
In a small bowl, beat together the cream cheese, granulated sugar, and vanilla until smooth. Set aside.
In a large mixing bowl, whisk together the melted butter, brown sugar, and granulated sugar until smooth and glossy.
Whisk in the egg, vanilla extract, and blueberry jam until fully incorporated.
Add the flour, baking soda, baking powder, and salt. Fold with a rubber spatula until just combined, being careful not to overmix.
Gently fold in the blueberries and white chocolate chips. If the dough feels too soft, refrigerate for 15–20 minutes.
Press about two-thirds of the cookie dough evenly into the bottom and slightly up the sides of the prepared skillet.
Spread the cheesecake filling evenly over the cookie dough, leaving about a ½-inch border around the edges.
Scatter the remaining cookie dough over the cheesecake in rustic pieces.
Sprinkle the cinnamon streusel evenly over the top.
Bake for 35–40 minutes, or until the edges are golden brown, the streusel is lightly browned, and the centre is just set.
Let the skillet cool for 15–20 minutes.
While the skillet cools, beat together the heavy whipping cream, icing sugar, and vanilla until medium peaks form.
Top the warm cookie skillet with homemade whipped cream and serve immediately. For an extra blueberry flavour, drizzle with warmed blueberry jam before serving.