For the crispy crust

1. Blend the margarine (or butter) until soft.
2. In another mixing bowl, put the flour together with the Zùsto and the sifted cocoa powder. Add this to the margarine and knead with your hands to form a dough ball. It will feel a little dry at first, but just keep kneading and it will be fine!
3. Take 2 sheets of baking paper and place the dough ball on them. Roll it out between the sheets of baking paper so the dough is a few millimetres thick. Allow the whole thing (dough + baking paper) to rest in the freezer for half an hour while you make the choux batter.

For the choux buns

1. Place the baking paper on the baking tray and preheat the oven to 180°C.
2. Place the milk, water, margarine, instant coffee and salt in a saucepan. Allow the margarine to melt completely and wait for it to bubble slightly. Remove the pan from the heat and freely add the flour. Mix with a wooden spoon to form a dough ball. Place over a medium-high heat again. The dough ball will now sizzle slightly. Turn the dough ball over a bit until the bottom begins to lightly burn (there will be a crust at the bottom of your saucepan). This is a good sign and means it is time to remove it from the heat. Put the dough ball in a bowl and allow to stand for a minimum of 15 mins before adding the eggs 
3. Add the eggs one by one (make sure your dough is no longer warm, or you’ll end up with an omelette :)). Make sure to mix it well between adding each egg.
4. Place the batter in a piping bag and cut a 1 cm opening. Pipe firm peaks onto the baking tray. The peaks I made were 5.5 cm tall because that was the size of my dough cutter. Although these do end up being giant choux buns! :).
5. Remove the dough from the freezer and cut out rounds (using the cutter) to the size of the piped peaks. Place a piece of dough on top of the buns.
6. Bake the choux buns for about 18 mins in a preheated oven. Want to check if they are done? Remove one from the oven and place it on a cooling rack. Does it collapse after about 30 seconds have elapsed? If so, the buns need cooking for a little longer and so continue to bake them for a few minutes longer. If it stays upright, you can remove the rest of them.
7. Allow the buns to cool completely on a cooling rack.

For the mocha batter

1. Whip the cream so that it becomes whipped cream.
2. In another mixing bowl, mix the mascarpone together with the Zùsto.
3. Dissolve the coffee in 1 tbsp hot water and add to the mascarpone mixture. Mix until the coffee is fully mixed into the batter.
4. Add the whipped cream to the mascarpone batter and then on a low speed, briefly mix the whipped cream into the batter.
5. Once the buns have completely cooled, you can cut off their “hats” with a sharp knife (or make it even easier on yourself and use scissors!). Put the mocha batter in a piping bag with a serrated nozzle and pipe swirls of batter into the buns. Cover with the hat.