In a small saucepan, combine half of the butter (4 oz), cocoa powder, salt, and water. Mix over medium heat until the sugar dissolves. Remove from heat and set aside.

Once smooth, add the remaining butter (2 oz) and whisk together.

Add the eggs one at a time, whisking until fully combined. Add the sour cream and vanilla, whisking until smooth.

Pour the batter into the prepared pan and bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean.

Cool in the pan for about 15 minutes, then invert onto a rack. Let it cool completely before adding the glaze.

While the cake is cooling, make the chocolate glaze: Place the chopped chocolate in a medium bowl and set aside.

In a small saucepan, combine the heavy cream, milk, and sugar. Heat over medium heat, stirring until the cream is hot and the sugar dissolves.

Pour the hot cream over the chocolate and stir until smooth. Add the vanilla.

Generously pour the glaze over the cooled cake. Cut into serving pieces and enjoy.