Preheat the oven to 350 degrees. Grease and flour a 9 x 13 inch baking pan.

In a large bowl, whisk together the cocoa powder, sugar, flour, salt, soda, and baking powder. (Note: If your cocoa powder is clumpy, you may need to sift it before whisking in).

Make a hole in the center of the dry ingredients then pour in the water, oil, vinegar, and vanilla.

Mix all the ingredients together until smooth. Pour in the prepared baking pan and bake for 32-38 minutes, or until the cake is starting to pull away from the sides and a toothpick inserted in the center comes out clean.

In a small sauce pan, melt the butter. Add the brown sugar and bring to a boil, whisking constantly, until sugar is dissolved.

Add the cream and bring back to a boil.

Remove from heat and sift 1 cup powdered sugar into the pot. Whisk until smooth. Continue to add powdered sugar until desired consistency is reached. (It should be thick, but pourable--like the consistency of maple syrup). Add the vanilla and salt.

Pour the glaze over the cake while it's still hot, then allow to cool on the cake.