A rich, white cream cheese that's easily spreadable, mascarpone is a key ingredient in tiramisu. When used in making tiramisu, mascarpone is usually mixed with eggs, sugar, whipping cream, salt and cream of tartar to make a mascarpone emulsion. Because mascarpone is high in fat, it's common for a mascarpone emulsion to separate or curdle. If you're making tiramisu and your mascarpone emulsion has started to separate, fixing it is simple.
Remove your mascarpone emulsion from any heat source at the first sign of separation. When your mascarpone emulsion starts to break down, you'll see small droplets of fat at the edge of the container in which you're mixing the emulsion. Though a mascarpone emulsion is typically mixed to prepare a tiramisu, which doesn't require heating, a mixing bowl at room temperature may cause enough heat to separate your emulsion, particularly if the mascarpone is high in fat.
Mix in 15 to 30 ml (1 to 2 tbsp) of flour and mix slowly. If you caught your mascarpone emulsion in the beginning stages of separation, this quantity of flour may be sufficient to bind the mixture. After adding the flour, slowly fold it into the mascarpone and double cream.
Add a drop of double cream and blend quickly if your mascarpone emulsion has completely separated. If your mascarpone emulsion has completely broken down, it will look grainy and thin. Add a small amount of double cream and blend quickly, using a hand mixer.