Reader Barry wants to know why, since pastry cream (another custard) is thickened with starch, Bavarian cream is thickened with gelatin. That’s a great question, and one I’m not sure I can fully answer. My feeling as that in centuries past, pastry chefs used whatever thickeners were available to them, so there were no hard and fast rules about it. However I will say that gelatin has an advantage over starch in that you can increase it in a recipe without compromising flavor or creating a “mealy” texture. It can also be melted and re-melted practically to infinity, and it will continue to set up perfectly, and that makes it a whole lot more versatile.
The problem I find, as I laid out at the beginning of this project, is that so often gelatin is used to excess, the result being custards that slice like aspics. That makes for a very disappointing charlotte or panna cotta to my mind, for instead of being creamy, they end up chewy. “Chewy” and “dairy” don’t really go together in my mind, at least when you’re talking dessert. For more on gelatin, see this post from a couple of years back.
UPDATE: Pastry Chef Laura points out that the big difference between the two is heat. Starch needs higher heat in order to gelatinize but gelatin needs very little. That makes it much more versatile, especially when you’re trying to set ingredients that don’t respond well to heat, like whipped cream or even other starch-based custards (creme chiboust, for example, calls for pastry cream as an ingredient along with meringue and gelatin). Excellent point, Laura — and thanks!