I would like to get a strong raspberry hit, so I tried the raspberry sauce that is in RHC, but it was too thin.
You mean the sauce on p.190? How did you use it, as a sauce served along side the cake?
What would be the best way to thicken it without losing the fresh, tart, sweet flavor?
This is the best way I know to make a fruit puree that tastes like fresh fruit, only more concentrated. Are you trying to thicken it to make it a stand-alone filling? Gelatin or agar would work for that.
Another possibility would be to get more raspberry flavor into the syrup. I’ve been using the milk chocolate syrup from the passion cake to syrup the cakes.
Hmmm, you could substitute eau de vie and/or raspberry essence for part of the milk, but be careful not to get it too hot or it will loose flavor. On the other hand, if the syrup is too cold it won’t penetrate well. Tricky. I must admit I’m wondering about the milk + raspberry combo. Perhaps consider the cream version of this syrup from the baby chocolate grands? And I’m not sure about substituting puree for part of the dairy, it might not penetrate very well if it’s too thick. And if you try to heat the milk with the puree, the acidity may curdle the milk.
Also, can I add eau de vie to the buttercream?
Which buttercream are you making, dreamy creamy, or the custard-based deluxe? Either way, there’s no liquid to substitute for, so it’s possible the buttercream could break. You might be OK with a dropper full of raspberry essence (La Cuisine), but that would tint the bc pink. Perhaps you could consider the white chocolate version of the mousseline buttercream in the Cake Bible? You can add raspberry eau de vie to that, no problem.
My personal choice on flavors would be to combine almond with the chocolate and raspberry, rather than hazelnut, but if you’ve made a test cake and the bride and groom love it, go for it.