Preheat the oven to 325°F (170°C or 160°C fan-forced). Line an 8×8 inch (20×20 cm) baking pan with aluminum foil, leaving an overhang around the edges. Lightly grease the foil.
Brownie Layer:
In a large bowl, add the chopped butter and finely chopped chocolate. Melt in the microwave at medium power (not high) in 45-second intervals, stirring between each until smooth. Alternatively, melt together using a double boiler.
Allow the mixture to cool slightly, then whisk in the whisked eggs, sugar, and vanilla extract until fully combined.
Whisk in the flour, cocoa powder, and salt. Sift the cocoa powder if it is lumpy. Set aside.
Pumpkin Pie Layer:
In another bowl, whisk together the pumpkin puree, evaporated milk, egg, vanilla extract, brown sugar, cinnamon, nutmeg, ginger powder, ground cloves, and cornstarch until smooth. Ensure there are no lumps of sugar or egg pieces. Optionally sift the cornstarch if it’s lumpy.
Assembling & Baking:
Spoon the brownie batter into the prepared pan and spread it evenly.
Carefully spoon the pumpkin mixture over the brownie layer, spreading it into an even layer. Be gentle to avoid disrupting the brownie layer.
Bake in the preheated oven for around 50 minutes, or until the pumpkin layer has a very slight wobble when you gently nudge the pan, but does not wobble like a liquid.
Remove from the oven and let the brownies cool completely in the pan. Then, place the pan in the fridge to chill for at least 2 hours, allowing the pumpkin pie layer to set.
When ready to serve, lift the brownies out of the pan using the overhang of the foil and place on a cutting board. Slice with a sharp knife, wiping the knife between cuts for clean edges.