stir everything together
Put vanilla sugar, pinch of salt and cornstarch to a medium saucepan. In a separate bowl whisk together milk and eggs. Pour the milk and eggs mixture to the saucepan with the dry ingredients. Using a whisk combine everything together to get a nice mixture without any lumps. Soak the gelatin in a cup with water for about 10 minutes.
Cook the pudding
Place the saucepan over high heat and add the butter (cut on small cubes). Incorporate the butter into the mixture using a whisk until there aren't any lumps and pieces left. Bring the pudding to a boil, whisking constantly (especially at the bottom of the saucepan). When the mixture starts to boil, cook for one minute, then remove from the heat, pour into two glasses and leave to cool to room temperature, for about 5 minutes.
Prepare the coffee surprise. Pour cooked unsweetened coffee (espresso) in a clean saucepan. Add the sugar and Amaretto liqueur. Place over medium - high heat for the sugar to dissolve. Occasionally shake the saucepan. Cook for about a minute, then remove from the heat and mix in the drained gelatin sheet. Pour a small amount of the coffee topping on top of vanilla pudding (at room temperature) then place in the fridge for at least 1 hour (or up to 24 hours) or in a freezer for about 15 minutes if you are in a hurry. Serve.