In a large bowl add the flour, sugar, salt and baking soda and mix together and set aside.
In a pan, melt the butter, then add the cocoa powder and water, stir and bring to a boil.
Take the butter/cocoa mix and pour into the bowl with the flour and mix together thoroughly.
In a small bowl, beat the eggs and the vanilla add the buttermilk (buttermilk can be made by adding a teaspoon of lemon juice or vinegar into milk and letting it sit for a minute).
Add the small bowl egg mixture into the larger bowl mix and incorporate together well.
Add the chocolate chips and mix again.
Take a a sheet pan and spray with cooking spray.
Place a cookie sheet under the pan if it is not sturdy (or disposable)
Pour the batter into the sheet and use a spatula to spread it out evenly.
Place into the oven and cook for 20-25 minutes, until testing with a toothpick comes out clean.
With a few minutes left to bake, start your frosting recipe.
Once done baking, remove from heat and when the cake it warm, pour the frosting all over the cake. Spread it out evenly and allow to cool slightly.
Frosting
In a pan, melt the butter.
Add the cocoa powder and milk and bring to a boil for 30 seconds.
Remove from the heat and add the vanilla and mix.
Add in the powder sugar. (I recommend sifting the powder sugar so you don't get lumps)
Stir until incorporated.
Pour onto the cake and spread out with a spatula until evenly all over the cake.
Sprinkle the mini chips on the cake and allow to cool.