Frozen. The term pasteis de nata is Portuguese for cream pastries. Pastel de nata are a traditional Portuguese pastry that can best be described as a kind of egg tart. They look a bit like little nests, with a thick outer layer of flaky pastry dough and a filling of rich yellow custard flavoured with cinnamon. The top of the custard is caramelized, with dark brown or black spots and a slightly different texture than the filling beneath it. The secret to making good Pasteis de Nata is to get your oven very hot and make sure you brown the tarts really well, almost to the point they look burnt. They are best eaten warm.