Make the brownies:
Place the bittersweet chocolate and butter in a heatproof bowl over a pot of simmering water.
Stir until fully melted.
Gradually whisk in the sugar and add the eggs one at a time, mixing well after each addition.
Add the cocoa powder and the pinch of salt.
Remove from the heat.
Gently fold the flour into the mixture with a rubber spatula and add the mini chocolate chips.
Pour the mixture into a square 9×9-inch cake pan that has been butter and lined with parchment paper, ensuring that excess parchment paper is hanging off of both sides.
Smooth the surface of the batter and bake at 350F for 60-80 minutes or until fully cooked.
Place the pan on a wire rack and allow the brownies to cool completely while still in the pan.
Then cut the brownies into 1-inch squares.
Make the pudding:
Place the sugar, cocoa powder and corn starch in a pot and mix to combine.
Gradually add the milk, stirring to combine.
Set to low heat and bring to a boil.
Boil for 2 minutes, stirring constantly, until thickened.
Remove from the heat and pour the pudding through a mesh sieve into a bowl.
Add the vanilla and stir to combine.
Cover the surface with a sheet of plastic wrap and place in the fridge until chilled, about 1 hour. Assembly:
Layer half of the brownies into the bottom of a clear bowl.
Drizzle with half of the hot coffee.
Note: if you don't drink coffee, you could use warmed up jam.
Spoon half of the pudding on top and spread out to create an even layer.
Layer the remaining brownies on top and drizzle with the remaining hot coffee.
Spread the rest of the pudding on top.
Place dollops of freshly whipped cream on top and top with some extra brownie pieces and chopped hazelnuts.