Is it a brownie? Is it a cookie? It's both! And also Fall-flavored! It's the Pumpkin Spice Mocha Brookie!
Preheat the oven to 350 degrees, place the oven rack in the center.
Butter and flour the cast-iron skillet.
For the pumpkin spice sugar:
In a small bowl, mix together the sugar and pumpkin pie spice. Set aside.
For the cookie dough:
In a medium mixing bowl, sift together the flour, baking soda, cream of tartar, 1 teaspoon of pumpkin pie spice and salt. Whisk to combine. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment (or using a hand mixer), add the butter and sugars.
Cream together on low speed, scraping the sides and bottom of the bowl as needed to fully incorporate. Add the egg and vanilla, and mix until combined.
Gradually add the flour mixture, and mix on medium speed until the flour is just incorporated. Set aside.
For the brownie batter:
In a large mixing bowl set over a saucepan of barely simmering water, add the butter and chocolate. Allow to slowly melt until smooth. Remove from the heat.
Using a hand mixer, whisk in the cocoa powder, espresso powder and sugar. Add the eggs one at a time, beating with each addition. Add the vanilla extract, then add in the flour and salt, beating just until fully incorporated.
In the prepared Smithey cast-iron pan, pour half of the brownie batter. Dump spoonfuls of the cookie dough on top and press down — don’t spread.
Using a small sieve, dust 1 tablespoon of the pumpkin spice sugar over the batter and dough. Cover the cookie dough with the remaining half of the brownie batter.
Then dump the remaining dough over the batter, again pressing down so that the brownie batter and cookie dough bake evenly. Dust with the remaining 1 tablespoon of spice-sugar.
Bake in the oven on the center rack for 30 minutes. Remove from oven and carefully cover with a sheet of foil and poke holes for ventilation.
Bake for another 10 minutes until a skewer inserted into the center of the brookie comes out clean.
Allow to cool in the pan for 20 minutes. While the brookie cools, make the chocolate sauce.
In a large bowl set over a pan of barely simmering water, add the chocolate and cream. Stir occasionally until fully melted and smooth.
To serve: Pour the chocolate sauce over the brookie. Top with scoops of vanilla ice cream. Serve immediately.