Add all pumpkin swirl ingredients to a blender and blend until smooth. Set aside.
Preheat your oven to 180°C and line a 20*30 cm rectangular pan with parchment paper (you can use a square 20*20 cm pan but brownies will be slightly thicker).
In a large bowl, mix together the flour, cocoa powder, sugar, baking powder, salt and vanilla.
Add the eggs, milk, melted chocolate and pumpkin puree. Whisk everything until smooth.
Pour batter in your prepared pan and dollop the pumpkin swirl mixture on top with a spoon. Using a toothpick, create swirls while linking the dollops or dots.
Bake in preheated oven for 25-30 mins or until firm to touch. Let cool before slicing.