For the cake:
Preheat the oven to 350F. Butter and flour an 8 inch cake pan and set aside. Combine all wet ingredients, as well as all dry ingredients, and whisk the wet ingredients into the dry ingredients one third at a time. Pour into the cake pan and bake for 45-55 minutes, or until a cake tester comes out of the center clean. Let cool for 15 minutes before removing from the pan, and then cool completely.
For the filling:
Combine the milk and cream and bring to a simmer. Remove from the heat and add the chocolate. Whisk until combined. Once all the chocolate has melted whisk in the butter. Let cool completely.
For the glaze:
Combine the gelatin and cold water and mix until dissolved. Combine the cocoa powder and water and mix to form a paste. Combine the sugar and heavy cream and cook over medium heat until it reaches a simmer. Add the cocoa powder mixture and the gelatin mixture and cook until hot to the touch, approximately 5 minutes. Note – the glaze must be kept warm until ready to use so it is best made once you are ready to glaze the cake.