Preheat the oven to 350 degrees. Spray two 8” cake pans (for best results use baking spray containing flour) and set aside.
In a small bowl, whisk together the flour, cocoa powder, baking soda and baking powder. Set aside.
In a large bowl, cream the sugar and butter together until light and fluffy, about 2 minutes.
Add in the eggs and vanilla, beat for an additional minute.
Alternate adding the flour mixture and the buttermilk, starting and ending with the flour. Do not overmix, just enough to see that the flour has been fully incorporated.
Once the flour and buttermilk are mixed in, add in the hot water (or coffee) and stir.
Divide evenly between the cake pans and bake for 30-35 minutes, testing with a toothpick until it comes out cleanly. Allow to cool in the pans for about 10 minutes before removing and allowing to cool completely.
While the cakes are cooling, make the cream filling.
In a small saucepan over medium/low heat, add the milk, flour and salt and whisk it together to prevent any lumps. Whisk continually while cooking to prevent any scorching until the mixture starts to thicken.
Remove from heat and whisk in the vanilla and set aside to allow to cool.
In a stand mixer (can be a hand mixer as well) place the butter and sugar and beat it for 5 minutes until it’s fluffy.
Add in the cooled milk mixture and continue to beat for another 5 minutes. The cream should be very fluffy.
Once the cakes are cooled, stack the bottom layer on cake stand** and scoop the cream filling on top.
To make a uniformed look, try to spread the cream in an even layer, leaving a small amount of space at the edge so the cream doesn’t spill over when adding the next layer.
Stack the top layer upside down, to create a smooth top to the cake. Fill in any gaps with cream if you notice it doesn’t reach the edges of the cake, or scrape any excess off that may have been pushed out by stacking the layers.
To make the ganache, heat the cream in the microwave and pour over the chocolate chips in a bowl.
Let it sit for about a minute and whisk until smooth. Add in the corn syrup and salt and whisk until smooth.
Let it cool slightly before gently spooning over the top of the cake, allowing it to slide down the sides and coat the entire cake.
Run the spoon over the sides to assist in coating if necessary. Wipe any excess chocolate off the cake stand if desired before serving.
Store any leftovers in an airtight container for up to 4 days.