Add <quantity>1<unit>L</unit></quantity> of heavy cream to a pot and heat it over low heat until it reaches <temperature>85<unit>°C</unit></temperature>

Add <quantity>½<unit>tsp</unit></quantity> of citric acid powder and stir to combine. Let it cook until it reaches between <temperature>80<unit>°C</unit></temperature> and <temperature>82<unit>°C</unit></temperature>

Transfer to another container and let it cool for 3h or until it reaches <temperature>44<unit>°C</unit></temperature> at room temperature

Place the cream in the refrigerator overnight to thicken

Place the cream through a sieve lined with a cheesecloth, set over another container

Place the cream in the refrigerator overnight to drain

Discard the liquid or save it for other preparations, and transfer the cream to another container. The mascarpone cheese is ready

Now you're all set for making a tiramisu!