Step 1

Preheat oven to 350 degrees and thoroughly grease a large baking sheet (we used a 12x18).

Step 2

Add the butter and water to a medium sauce pan and bring to a boil. Stir to combine then remove from heat.

Step 3

In a large bowl, combine flour, sugar, salt, and baking soda and whisk together.

Step 4

Pour the butter mixture into the dry ingredients and mix until smooth.

Step 5

Add vanilla, sour cream, and the eggs to the batter and mix while scraping the sides of the bowl.

Step 6

Pour batter into prepared baking sheet to form one level layer.

Step 7

Bake for 17-20 minutes or until a inserted toothpick comes out clean of batter.

Step 8

Once the cake is finished baking, start on the frosting.

Step 9

In a microwave safe bowl, melt butter.

Step 10

Add 2 cups of the powdered sugar, sour cream, salt, and vanilla. Mix until there are no lumps.

Step 11

Add remaining powdered sugar and mix until incorporated.

Step 12

After cake has cooled for 20 minutes, pour frosting over cake and spread into an even layer.

Step 13

Allow cake to cool for at least 1 hour (until frosting sets) before cutting.