The secret recipe of these famous custard tarts of the Belem district of Lisbon is well protected. Throngs of visitors to the bakery line up to enjoy the luscious custard tarts. If you time it right, you can watch through a window while the pastries are formed. While I do not have the secret recipe, I have published two versions of the tarts. The first one, taught to me by a baker who learned it in a culinary school in Lisbon, is given in detail in my first book, Portuguese Homestyle Cooking under the title of Custard Cream Pastries/ Pasteis de Nata. Its texture and taste is very close to what I enjoyed at the Belem bakery.
In my newest book, Authentic Portuguese Cooking, I have given a shorter recipe under the name of Custard Tarts Belem Style/ Pasteis de Nata. Check out the step by step recipe in the book. Feel free to contact me with questions about recipes.