Preheat oven to 375°F. Butter a 16x10x1 inch baking pan (or Baker’s half sheet pan.)
Mix flour and sugar in a large mixing bowl; set aside.
In a saucepan, combine butter, cocoa, and water; bring to a boil and take off heat.
Stir the butter/cocoa mixture into the flour/sugar mixture. Add sour cream, eggs, vanilla, baking soda and salt. Mix well.
Pour into prepared pan. Bake 15-20 minutes or until cake tests done.
In a large saucepan, melt butter on medium heat, sauté vegetables until translucent.
Stir in liquid gradually and bring to a boil over high heat. Cover and reduce heat to simmer for 3 minutes.
Turn off heat, add dressing mix and blend lightly. Cover and let stand for 5 minutes. Fluff with fork and serve.
Spread icing over cake as soon as it comes out of the oven.