Preheat oven to 325 degrees and grease a 10 inch bundt pan.
In a medium bowl, combine the cake mix, pudding mix, eggs, water, Rum, and vegetable oil. Mix until combined.
Pour batter into prepared bundt pan.
Bake in preheated oven for about 1 hour.
Remove cake from oven and allow to cool for about 25 minutes.
Turn cake onto a serving plate.
Poke small holes into cake (along the top especially).
To prepare glaze, melt butter in a saucepan over medium heat. Stir in the water and sugar. Boil for about 5 minutes. Remove from heat and stir in the Rum.
Pour glaze evenly on top of the cake, making sure to get it into the small holes as well.
To prepare the chocolate glaze, melt chocolate and butter/shortening over low heat in a sauce pan.
Once cake has fully cooled, drizzle the chocolate on top. Sprinkle with nuts (if using) while chocolate is still somewhat wet.
Serve cake and enjoy!