Preheat oven to 350° F.
In a large bowl, whisk together the dry ingredients - flour, sugars, cocoa powder, baking powder, baking soda, and salt.
In a separate bowl, melt the chocolate in the microwave in 15-30 second bursts, stirring each time. When fully melted, set aside to cool.
Once the melted chocolate lightly warm or cooled, add the oil, eggs, vanilla, unfed sourdough starter, and whisk vigorously together or beat together with a hand mixer until well combined.
Add the mixed wet ingredients to the large bowl of dry ingredients and gently mix together. Add the hot water last and mix together until everything is combined and smooth.
Spray a bundt pan generously with nonstick spray. Optional, but an additional assist to ensure a nonstick bundt pan is to sift in cocoa powder to the main portion to the bundt pan.
Pour the batter into the prepared bundt pan and bake in the oven for about 38-42 minutes, or until moist or no crumbs come out on a toothpick.
Keep it in the bundt pan for 5-10 minutes until you see the edges of the cake release from the sides of the pan. Transfer to a cooling rack. You can do this by placing a cooling rack on top of the bundt pan and then holding it all together, flip it over swiftly and gently.
Glaze: Prepare the glaze by first beating together the softened cream cheese and melted butter. Add cocoa powder, powdered sugar, and vanilla; beat again. Lastly add heavy cream until desired consistency. You can also warm it up in the microwave for 15-30 seconds at a time to assist with the glaze-like consistency. When cake is still slightly warm or cooled, use a large spoon to dress the cake with the chocolate glaze. Store at room temperature. Enjoy!