Prep the Pan

1. Spritz a 9×13 pan with a little cooking spray, and then line the bottom of the pan with a piece of parchment

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Melt the Butter

1.  Melt the butter with the water, milk, and cocoa.
2. Once the water boils, whisk out any lumps in the cocoa and butter until smooth.

Mix the Dry Ingredients

1.  Stir together the sugar, flour, baking soda, and salt together in a small bowl. Adding the sugar with the flour will keep the flour from getting lumpy in the cake batter.
2. Add the dry ingredients into the hot buttery cocoa water and stir until everything is moistened.

Finish the Batter

1.  Crack the eggs into a small bowl and break them up with a fork.
2. Add the eggs and vanilla to the batter and stir just long enough for all the flour to disappear and to create a smooth batter.

Bake the Cake

1. Scrape the batter into the prepared pan.
2. Bake for 28-30 minutes for a 9×13 pan, about 18-22 minutes for a half sheet pan and about 15-20 minutes for a jelly roll pan.
3. While the cake is making, make the glaze.

Make the Glaze

1.  Bring the sugar, half and half, and butter to a boil in a small pan over medium heat.
2. Whisk everything once the mixture starts boiling, and then let it boil for 1 minute.
3. Turn the heat off and add in the chocolate chips.
4. Stir periodically until the chocolate melts and the glaze is smooth.

Finish the Cake

1.  Let the glaze cool until warm and then pour it over the top of the cake. 
2. Top the cake with sprinkles if you’d like.
3. Cut the cake into 15 pieces (or more) for serving.