Preheat oven at 180xb0C. Grease and flour a loaf tin.
In a large bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, chai masala. Using a fine grater, grate roughly 1/2 tsp of nutmeg into this. You can use readymade nutmeg powder, but freshly grated nutmeg will provide a far more intense aroma
Cream together the butter and sugar. Whisk in butter milk. If buttermilk is cold, the butter will solidify somewhat, but this is okay
In a blender/mixer, blend together the pumpkin puree, creamed sugar, and buttermilk mix
Add this to the dry ingredients. Bring together gently with a spatula. Don't overmix
Pour 2/3rd of this mix into the prepared loaf tin
To the remaining batter, add the cocoa or Nesquick, thin it with 3 tbsp of milk until it is of cake batter consistency
Add this over the top of the pumpkin batter layer. With a toothpick or chopstick inserted right into the cake batter, swirl the batter, poking it into the bottom layer in multiple places. This is what gives the marbling effect
Sprinkle walnuts and gently press them down
Place in the middle rack of a preheated oven to bake for 35-40 minutes, until a tester comes out clean
After 2-3 minutes, carefully loosen the edges and invert over a wire rack, where you can let it cool for 30 minutes or so, before slicing
Serve warm with coffee or tea.