Preheat the oven to 350 F (180 C).
Grease a 9×13 inch (23 cm x 33 cm) rectangular pyrex dish. Set aside.

In a medium saucepan, combine the butter, water, and cocoa.
Cook over medium heat until the butter and chocolate have completely melted.

Add the flour, sugar, salt, baking soda, eggs, and sour cream to the butter-water-cocoa mixture. Mix well.

Pour the batter into the prepared pyrex dish. Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean.
Remove from the oven.

Glaze:
In a small saucepan, combine the butter, milk, and chocolate. Melt over medium heat. Stir in the sugar, vanilla, and pecans and mix until well combined.
Pour over the warm cake, spreading evenly.
Let cool and cut into squares.