Preheat the oven to 350°F and grease an 8x11 baking dish generously with coconut oil or cooking spray.

In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt until fully combined. Add the milk, neutral oil, apple cider vinegar, and vanilla extract and whisk until smooth and no lumps remain. Pour in the hot coffee and whisk until fully incorporated.

Pour the batter into the prepared baking dish and bake for 28–32 minutes until a toothpick inserted in the center comes out with just a few moist crumbs. Do not overbake or the cake will be dry. Let cool completely in the pan before adding any toppings.

While the cake cools, make the ganache. Combine the dark chocolate chips, milk, chocolate hazelnut spread, coconut oil, and salt in a microwave-safe bowl. Microwave in 30-second intervals, stirring between each, until completely smooth, silky, and glossy — about 60–90 seconds total. Let cool for 5 minutes until slightly thickened but still pourable.

For the cornflake crunch, combine the chocolate hazelnut spread and melted chocolate in a large bowl and stir until fully combined and smooth. Add the cornflakes and fold gently until every single cornflake is completely coated in the chocolate mixture.

Once the cake has cooled completely, pour the ganache generously over the top, spreading it to the edges and letting it pool slightly. Immediately pile the chocolate cornflake crunch generously over the ganache while it's still slightly warm and soft so the cornflakes adhere and nestle into the ganache as it sets.

Let sit for 15–20 minutes until the ganache is set enough to hold the cornflakes in place. Serve directly from the baking dish with a large spoon. This cake is meant to be scooped, not sliced cleanly.