Some time ago someone had mentioned to me how they thought Chinese egg tarts (dan tat) were a bit of a weird dessert. I said something to the effect, "Do you think creme brulee is a weird dessert?" They responded no, then I said, "then it's not a weird dessert, you're just not used to that kind of dessert at a Chinese restaurant or with dim sum."
The conversation then moved into the differences between various milk / cream with egg desserts. The reality is so many desserts have only minor variations from each other. So the weirdness really comes from the unfamiliarity with it in a certain cuisine or in a certain restaurant.
I was reminded on this conversation after making some pot de creme and decided to recall the differences. The internet is not too helpful on some of the detailed differences (everyone has their own recipe, globalization / commercialization has changed recipes over the years), but here's my minimally researched summary on all the differences.
The main difference between all of these desserts is the ratio of milk, cream, sugar, and eggs (and if it uses egg yolks or whites or both). I don't mention the ratios or the specific cooking technique, it's just to give the basics. I don't mention flavoring, which all of the below can add whatever flavoring you want (vanilla, chocolate, lemon, etc.).
Here we go with the dessert list.
custard - milk / cream & sugar and egg yolks used to thicken it
creme brulee - custard with a caremalized sugar topping
flan - custard with a caramel sauce topping
pot de creme - a lighter custard
pastry cream - an even lighter custard, usually done by using only milk and/or using only egg whites. Use this in ...
cream puff - pastry with pastry cream in it
bavarian cream - pastry cream, but add whipped cream to make it lighter.
mousse - like custard, but instead of cream / egg straight up, add whipped cream / whipped egg whites to make it lighter and airier.
semifreddo - mousse but you freeze it
ice cream / frozen custard - you basically start with a custard, then you churn / freeze it (modern day ice creams in stores may not add eggs, as they may use other thickeners)
gelato - different ratios than ice cream, leading to denser / less airy form
Portuguese egg tart / pastel de nata - custard in a puff / pie crust, and slightly caramelized on top
so ... how is Chinese egg tart different?
Chinese egg tart (dan tat) - custard in a puff / pie crust, usually less sweet. No caramelization on top compared to pastel de nata. The internet can't seem to agree if the custard is denser or lighter, I'm sure every restaurant / region has a variation.
And I'll add one more Chinese dessert that hasn't really gotten a foothold in Western countries.
Chinese steamed pudding - milk with egg whites as thickener
at the end of the day? How different are these desserts really?
To finish up this post, for fun, how about a few other desserts that are similar, but just use non-eggs as thickeners.
pudding - milk & sugar with flour / cornstarch used as thickener
panna cotta - milk / cream & sugar and gelatin as thickener