Preheat oven to 175℃.
Grease and flour an 8 inches by 4 inches loaf tin (at least 3 inches deep).
Measure the butter into a large bowl and cream until soft.
Add the brown sugar and continue to beat until the mixture turns light and fluffy. This should take at least 2 minutes on medium speed. Scrape the sides of the bowl halfway through.
Next, add the eggs, one at a time (see Note 1). Each time, beat until all traces of the egg are no longer visible. Do not overbeat. Scrape the bowl and mix well.
In a separate bowl, measure the flour, baking powder, salt and the pumpkin spices. Stir with a hand whisk until well combined.
Sift one third of the flour mixture into the creamed butter, sugar and eggs. Fold with a spatula until well combined (see Note 2).
Next, add half of the milk. Fold well.
Repeat the process with another one third of the flour mixture, followed by the remaining milk and then the last one third portion of the flour mixture. Scrape the sides and bottom of the bowl and the spatula and mix well.
Add the vanilla extract. Fold well.
Remove one third of the prepared cake batter into a separate bowl. Sift in the black cocoa powder and mix well (see Note 3). Rest the batter for 2 to 3 minutes to see the color of the dough as the black color of the cocoa powder will intensify after a few minutes. If it is not sufficiently black, add a few drops of black gel food coloring and mix well (see Note 4).
Sift in the pumpkin powder into the remaining batter and mix well. Add a few drops of orange food coloring to intensify the orange color of the batter (see Note 4). Mix well.
Spoon the cake batters alternately in the prepared tin. Start with a layer of orange batter. Level it with a spatula.
Next, drop small spoonfuls of the black batter onto the orange batter in random order.
Top with scoops of the orange batter followed by more black chocolate batter until all the black batter is used up.
Finally, top with the remaining orange batter and level it with a spatula. Use a skewer to cut through the cake batter to create swirls and marble pattern in the batter. Start with horizontal lines, followed by vertical lines and then diagonal lines.
Bake the cake in a preheated oven until a cake tester or wooden skewer inserted in the center of the cake comes out without any wet batter. Remove the cake from the oven and let it rest in the cake tin for a few minutes before turning it out onto a wire rack to cool it completely (see Note 5).
To make the glaze, sift the powdered sugar (see Note 3) into a small bowl. Add water and mix well.
Place the completely cooled cake on a cake plate or cake board.
Transfer the prepared sugar glaze into a piping bag and snip the tip. Drizzle the glaze on the cake, forming drips from the edges of the cake.
To complete the cake decoration, sprinkle the orange and black sprinkles all over on top of the cake and decorate with candy eyes (see Note 6).