I made a tiramisu cake for my husband’s birthday in October and I added gelatin to the mascarpone filling to thicken it up. It worked wonderfully and the texture was like a mousse. I followed the instructions on the knox gelatin package (measured the amount of liquid filling and added the gelatin to it) But for the traditional tiramisu, that might be too thick, But maybe a little bit of gelatin added to the mascarpone filling might just be enough for you, if you want it a bit thicker.
But, If the egg yolk mixture didn’t triple in volume, or the cream wasn’t whipped to stiff peaks, you filling would definitely be thinner. I’m sorry but I can’t remember what the consistency of my filling was before I added the gelatin. I was also thinking that when you fold in the whipped cream into the mascarpone filling you need to be gentle and don’t over do it. Fold it gently until well blended. It you stirred it maybe it might deflate the whipped cream resulting in a thinner filling. But if everything was done correctly and it was still to thin for your liking I don’t see why you could not add a little bit of gelatin to thicken it up. One package of gelatine is per-measured to set 2 cups of liquid. You would have to experiment with the amount of gelatin you would need for the filling. Maybe make up a small batch of filling and add half the amount of gelatin and see what the consistency is like. If it is too thick, next time add less, if it is too thin add a little more, until you have the consistency you want. Trial and error. You could use the filling to top sliced vanilla pound cake and add grated chocolate ontop to use up your small batch. Don’t throw it out!! It tastes so good!!!
