Preheat your oven to 350°F (175°C) and grease two 8-inch round cake pans.

Combine 1 cup of milk with 1 tablespoon of white vinegar and let sit for 5 minutes.

In a large bowl, whisk together the curdled milk, 0.5 cup vegetable oil, and 1 cup cane sugar until smooth.

Sift together 1.5 cups flour, 0.75 cups cocoa powder, 1 teaspoon baking soda, 1 teaspoon baking powder, and a pinch of salt.

Gradually mix the dry ingredients into the wet mixture until fully incorporated.

Pour in 1 cup of boiling water or freshly brewed coffee and stir until smooth.

Divide batter between prepared pans and bake for 25-30 minutes.

In a medium saucepan, combine 1 cup chocolate milk, 0.67 cups sugar, 0.75 cups cocoa powder, and 2 tablespoons cornstarch over medium heat.

Cook while stirring until thickened, about 8-10 minutes; add butter, vanilla extract, and salt.

Remove from heat, mix in 4 ounces of dark chocolate, and refrigerate for 2-3 hours.

Assemble the cake by spreading custard between layers, crumb coating, and chilling for 30 minutes.

Apply a final layer of custard and refrigerate for another 30 minutes before slicing.