First, preheat the oven to 375°F. Grease a half sheet pan (13”x18"x1”) with baking spray.
Using a microwave safe bowl, melt the butter in the microwave in intervals then set aside to cool.
In a separate large bowl add the sugar, flour, baking soda, and salt and whisk together until well combined.
Then, add the eggs to the cooled, melted butter and whisk until combined.
Combine the sour cream, milk, and vanilla in another large mixing bowl. Then add the butter mixture to this and whisk until combined.
Add the dry ingredients to the butter mixture and whisk until just combined. You may need to add in sections to make combining easier.
Add half of the mini chocolate chips to the batter and stir so they end up well-dispersed.
Pour batter into the prepared baking pan and sprinkle the rest of the mini chocolate chips on top.
Bake cake for 20-25 minutes or until it's golden brown. Then allow it to cool completely before frosting with homemade ganache.
To make the homemade ganache: In a microwave-safe bowlcombine cold heavy cream, 8oz semi-sweet chocolate chips, and corn syrup.
Heat in the microwave on high for 30 seconds. Stir well until the cream starts to turn brown from the chocolate. Heat for about 30 more seconds. Stir until smooth.
Frost cooled cake with freshly made ganache. Sprinkle half a bag of mini chocolate chips on top, if desired.
Cut and eat cake immediately or refrigerate until ready to serve.