In a large mixing bowl, combine flour, sugar, baking soda, cocoa powder and salt. Combine well.
Next add eggs, milk and butter. I add a dash of vanilla extract sometimes but optional.
On low, mix until well combined, turn mixer to high and whip until fluffy. About 2 minutes.
Preheat oven to 350. In a 9x13 baking dish, spray with non stick spray. Add cake mix and smooth evenly.
Bake for 20 to 25 minutes or until toothpick inserted in middle comes out clean.
Cool on wire rack.
While cake is cooling, mix filling ingredients until light and fluffy. Whip on high until smooth.
When cake is completely cooled, either cut into circles with biscuit cutter and split in half, or rectangles for individual servings. Cut in half. Spread filling between layers. Top with other half.
I also just cut cake in half, cut each half into 2 layers and fill in between layers. You can also just use filling as frosting.
