Dough: Combine light brown sugar, lukewarm oat milk and yeast together. Set aside. Combine melted vegan butter and vanilla extract together. Once the oat milk mixture becomes foamy, combine it with the slightly cooled butter mixture. Pour over the flour and combine. Knead on a lightly floured surface for around 5 minutes or until it's no longer sticking to clean dry hands. Grease a clean bowl, and the dough ball with around 1/2 tbsp butter. Place the greased dough ball, into the greased bowl. Cover with a tea towel, and set aside for 45 minutes or until doubled in size.
Filling: In a small bowl, mix the cinnamon, light brown sugar and granulated sugar together. In another bowl, combine the softened vegan butter and vanilla extract. Roll dough out onto a lightly floured surface into a 12 x 17-inch rectangle. Leaving a slight border, spread that vanilla butter all over the dough. Sprinkle the cinnamon sugar mixture, and then the small chopped dark chocolate chunks. Make sure you also use up all those small, dust-sized pieces of chocolate! Tightly roll into a log. With dental floss or a piece of thread, cut the log into 12 equal-ish rolls. Place into a pre-lined baking tray. Cover with the same tea towel, and set aside for another 45 minutes. Pre-heat the oven to 180°C/356°F.
Baking: In a small bowl, combine 3 tsp oat milk, 1/2 tsp maple syrup and a pinch of cinnamon. Brush all over the chocolate cinnamon rolls before baking (Use it all!). Pop into the oven and bake for 25-35 minutes. For the softest buns, cover with a tea towel for 20 minutes as soon as they come out of the oven.
Icing: In a medium saucepan, combine vegan butter and maple syrup, Once the mixture starts to bubble, mix in the instant coffee. Turn off the heat, and then mix in the icing sugar. Allow to cool slightly before drizzling over the freshly baked buns. Enjoy!