Preheat your oven to 400 degrees Fahrenheit.
Grease four 6-ounce ramekins generously with butter and dust with cocoa powder.
Melt the chocolate in a double boiler or microwave until smooth and set aside to cool slightly.
In a large bowl, whisk the eggs, egg yolk, and brown sugar until thickened.
Fold the cooled melted chocolate into the egg mixture until fully combined.
Stir in the flour, cocoa powder, pumpkin pie spice, and salt until just incorporated.
In a separate small bowl, lightly stir the pumpkin puree to ensure it is smooth.
Fill each ramekin halfway with the chocolate batter, add a dollop of pumpkin puree in the center, and cover with the remaining chocolate batter.
Bake for 12 minutes until the edges are set but the center remains slightly soft to the touch.
Let sit for 1 minute before inverting onto plates to serve warm.