Tiramisu is a classic Italian desert made from layers of mascarpone custard and sponge fingers, or "lady fingers." While there are many variations on the recipe, some adding fruit, others drenching the sponge in liqueur or piling high with cream, the mascarpone custard remains a constant throughout. The only trouble is that the delicate, silken custard has a tendency to break, or curdle. Happily, it is possible to fix a broken tiramisu.
Let the broken tiramisu custard sit for around 15 minutes so that it comes to room temperature. The primary reason for tiramisu custard to break is that the ingredients (egg yolks, mascarpone cheese, sugar and cream or egg whites) are combined at different temperatures.
Whisk the broken mixture slowly, adding a dusting of plain flour as you go.
Continue lightly whisking and adding up to 2 tbsp. of plain flour until the broken mixture emulsifies again. Continue with constructing the tiramisu according to your recipe.