Giant King Cake Pop-Tart®

Preheat the oven to 400 degrees F (200 degrees C). Line a half-sheet pan with parchment paper.

Mix brown sugar, butter, flour, cinnamon, and salt together for the tart in a medium bowl with a fork or clean hands until thoroughly combined. Set aside.

Whisk egg and water together in a small bowl; set aside.

Lightly dust a clean work surface with flour. Place one sheet of puff pastry on the surface; gently pinch the seams of the sheet together. Lightly dust surface of pastry with flour and roll into a 9x13-inch rectangle.

Carefully transfer the puff pastry sheet to the prepared pan and prick the entire surface with a fork. Spread the brown sugar-cinnamon filling all over the puff pastry, leaving a 1-inch border around the edges. Use a pastry brush to brush this 1-inch border with egg wash.

Repeat rolling process detailed in step 4 with the second sheet of pastry. Using your rolling pin, carefully place the second sheet of pastry on top of the first, lining up the corners and edges. Seal the two sheets of pastry around the edges by pressing together with the prongs of a fork. Prick the entire surface with a fork and brush all over with egg wash.

Bake in the preheated oven until golden brown, 20 to 25 minutes. Cool for 10 to 15 minutes.

While the tart cools, beat cream cheese and butter together for icing until smooth. Beat in the powdered sugar until smooth. Beat in milk, 1 tablespoon at a time, until desired consistency is reached. Spread the icing over top of the tart. Decorate as desired with sanding sugars.