Prep the pan and oven: Heat the oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment, leaving overhang on the long sides so you can lift the bars out later.

Make the crust: In a bowl, combine graham crumbs, sugar, cinnamon, and a pinch of salt. Stir in the melted butter until the texture resembles damp sand.

Press and pre-bake: Firmly press the crust mixture into the lined pan in an even layer. Bake for 8–10 minutes until set and fragrant. Let cool slightly while you prepare the filling. Reduce oven temperature to 325°F (165°C).

Beat the cream cheese: In a large bowl, beat softened cream cheese with sugar and cornstarch on medium speed until smooth and fluffy, about 2 minutes. Scrape the bowl well.

Add eggs: Beat in the eggs one at a time on low speed, just until incorporated. Avoid overmixing to limit air bubbles.

Flavor it: Mix in eggnog, vanilla, rum or rum extract (if using), nutmeg, cinnamon, and a pinch of salt. The batter should be silky and pourable.

Pour and smooth: Pour the filling over the warm crust. Tap the pan gently on the counter to release any trapped air.

Bake low and slow: Bake at 325°F for 28–35 minutes. The edges should look set, and the center should have a slight jiggle, like set Jell-O.

Cool gradually: Turn off the oven, crack the door, and let the bars sit inside for 10 minutes. Remove to a rack and cool to room temperature.

Chill completely: Cover and refrigerate for at least 4 hours, preferably overnight, until fully set.

Finish and slice: Stir together the cinnamon and sugar for topping. Lift the slab out using parchment, dust with cinnamon sugar and a little grated nutmeg, then slice into bars with a sharp knife, wiping the blade between cuts.