This is "tarte au flan" in a miniature, richer and cinnamony-er version. Lots of egg yolks for a deep yellow soft set custard, with a slightly burnt sugar crust on top. The dough is flaky crunchy and buttery. No short crust here.
They are all over in Lisbon, on every cafe counter, and often served with a deep black expresso. These ones were still hot when bought them.
The trick I was told is to make the sides of the puff pastry crust thicker by taking a disk and flattening the center to push the dough to the sides.