Irresistible Creamy Dulce de Leche Bars

Preheat Oven: Preheat your oven to $175^\circ\text{C}$ ( $350^\circ\text{F}$ ).
Prepare Pan: Line an 8×8 inch or 9×9 inch square baking pan with parchment paper, leaving an overhang for easy removal.
Mix Dry: In a large bowl, whisk together the flour, granulated sugar, and salt.
Cut in Butter: Use a pastry blender or your fingertips to cut the cold butter into the dry ingredients until the mixture resembles coarse crumbs.
Press: Press the crumb mixture firmly and evenly into the bottom of the prepared pan.
Bake: Bake the crust for 20-25 minutes, or until the edges are lightly golden brown.

Quick Method (If starting with condensed milk): Pour the condensed milk into a shallow, oven-safe dish. Cover tightly with foil. Place the dish in a larger baking pan and fill the large pan with hot water halfway up the sides of the condensed milk dish.
Bake DL: Bake at $200^\circ\text{C}$ ( $400^\circ\text{F}$ ) for 1 to 1.5 hours, checking periodically and adding water if needed. The milk should turn a dark caramel color. Carefully remove, whisk until smooth, and set aside. (Alternatively, just use quality store-bought Dulce de Leche).

Combine (If using cream cheese): In a bowl, beat the softened cream cheese with powdered sugar and vanilla extract until smooth. Gently fold in 1 cup of the prepared Dulce de Leche (or Biscoff/Caramel). This creates the thick, solid layer seen in the photograph.
Spread: Pour the creamy Dulce de Leche filling evenly over the still-warm shortbread crust.

Second Bake: Return the pan to the $175^\circ\text{C}$ ( $350^\circ\text{F}$ ) oven and bake for an additional 15-20 minutes, or until the filling is mostly set and the edges are lightly golden.
Cool: Let the bars cool completely to room temperature on a wire rack. Then, transfer the pan to the refrigerator and chill for at least 3 hours (or overnight). Chilling is essential for clean, neat slices.
Drizzle: Once chilled, use the parchment paper overhang to lift the bars out of the pan. Place on a cutting board. If desired, heat the remaining caramel sauce slightly and drizzle it decoratively across the top of the bars, creating the sleek lines seen in the image.
Slice: Cut into neat square bars using a sharp knife dipped in hot water between cuts.