Place rack in the lower third of your oven and preheat the oven to 350 degrees F. Lightly grease a 9 to 12-inch ovenproof skillet (it does not need to be cast iron, just oven safe up to 350 degrees).
For the brownie batter: Melt the butter in a medium saucepan set over medium heat. Add the brown sugar, then stir to combine. Let heat for about 30-60 additional seconds, until the mixture is beginning to bubble and a bit more of the sugar has dissolved. Remove from the heat, then stir in the cocoa powder, baking powder, salt, espresso powder, and vanilla. Let cool for a few minutes, until the batter feels warm but not uncomfortably hot when touched with your finger.
Whisk in the eggs one at a time, fully incorporating between each addition and stirring until the mixture is shiny. Add the whole wheat flour, stirring until the batter is smooth once more, then stir in the chocolate chips. Set aside.
For the pumpkin cheesecake batter: In a large mixing bowl, beat the cream cheese and pumpkin together until smooth and no lumps remain. Beat in the granulated sugar, all purpose flour, and spices until smooth and combined. Beat in the vanilla and egg.
Spoon half of the brownie batter into the prepared skillet. Smooth the top with a spatula, then dollop 2/3 of the pumpkin cheesecake batter on top. Dollop on the remaining brownie batter to create patches, then the remaining pumpkin cheesecake batter.
With a butter knife, gently swirl the layers together, being careful not to overmix. Work quickly so that the batters do not set.
For a 10-inch skillet, bake for 35 to 45 minutes (see notes), until a toothpick inserted in the center comes out with only a few wet crumbs clinging to it (do not overbake!) and the edges are set. Check the brownies at the 20-minute mark—if you feel the top is brownie too quickly, lightly tent with foil, then continue baking as directed. Let cool, then cut into wedges and enjoy.
*If you are using a skillet that is smaller or larger than 10 inches, you will need to adjust the baking time. Brownies baked in a larger skillet will cook more quickly, while those baked in a smaller skillet will need a few additional minutes. Keep an eye on your skillet and check a few minutes early to ensure the brownies do not overbake.
**This recipe can also be baked in a 9-inch square baking pan.
TO STORE: Keep cooked and cooled brownies in an airtight storage container in the refrigerator for up to 3 days.
TO FREEZE: Store brownies, wrapped tightly in plastic, in the freezer for up to 3 months.