Preheat oven to 350°F (180°C). Line an 8x8-inch baking pan with parchment paper.
In a large mixing bowl, beat the cream cheese until smooth. Add pumpkin puree, sugar, egg, vanilla, salt, pumpkin pie spice, and cinnamon. Mix until creamy and well combined.
8 ounces cream cheese, 1 cup pumpkin puree, ½ cup granulated sugar, 1 large egg, 1 teaspoon vanilla extract, ¼ teaspoon salt, 1 teaspoon pumpkin pie spice, ½ teaspoon ground cinnamon
In a separate bowl, prepare the brownie batter according to package directions. Stir in ¾ of the chopped dark chocolate.
1 box (16.3 ounces) fudge brownie mix, 4 ounces dark chocolate bar
Spread ¾ of the brownie batter evenly in the prepared pan. Alternate spoonfuls of the pumpkin mixture and the remaining brownie batter on top.
Use a butter knife to gently swirl the two batters together for a marbled effect. Sprinkle the rest of the chopped chocolate over the top.
Bake for 45–50 minutes, or until the edges are set and a toothpick inserted near the center comes out mostly clean (a little pumpkin on the toothpick is okay).
Allow to cool completely in the pan before slicing into squares.