Step 1

In a large bowl, mix together the cake mix, egg, melted butter, and nutmeg (if using).

Step 2

In a 7x9 baking pan lined with parchment paper, press the batter in an even layer.

Step 3

In a large bowl, stir together the softened cream cheese, eggs, and vanilla extract.

Step 4

Stir in the powdered sugar.

Step 5

Pour this frosting batter over the top of the cake batter layer.

Step 6

Bake at 350°F for 45 minutes. The edges will puff slightly and turn golden brown, while the center will remain very jiggly.

Step 7

Remove from the oven and allow the cake to cool.

Step 8

Refrigerate for at least two hours (covered) or overnight before cutting into bars.