Preheat your oven to 325°F (160°C), no fan.
Add gingerbread spice mix, cinnamon, cocoa powder, honey, sugar, butter, oil, plum preserves, salt, and ground coffee into a medium/large pot and heat over low heat until all the ingredients are well-combined and hot but not boiling.
Add the milk, heat over low heat, whisking until all the ingredients are well-combined and warm. Take the pot off the heat and add the eggs, whisk until combined.
Whisk in baking soda.
Sift the flour into the pot. Whisk until just combined (don't overmix the batter).
Pour the mixture into a 9x5 inch loaf pan (23x13 cm or similar) lined with parchment paper.
Bake for about 1 hour and 5 minutes or until a cake tester/wooden skewer comes out clean.
Place the cake on a cooling rack and leave it to cool for at least 30 minutes.