Combine flour and sugar in a large bowl or stand mixer bowl. Add softened lard or margarine, baking ammonia or baking powder, and your chosen flavoring (vanilla or lemon zest). Mix until the fat is evenly worked into the dry ingredients and the mixture looks sandy.

Add the eggs one at a time, mixing after each addition until the dough comes together. Shape it into a log, wrap it well, and chill for at least 4 hours or overnight for better texture.

Warm the milk in a saucepan until hot but not boiling. Whisk yolks with sugar and chosen flavoring in a bowl, then whisk in rice starch and cornstarch until smooth. Slowly pour this mixture into warm milk while stirring constantly. Cook over gentle heat until thickens and bubbles appear. Scrape into a bowl, cover with plastic wrap, and refrigerate until fully cold.

Preheat oven to 350°F and grease molds. Cut chilled dough into discs, rolling out half to press into base of molds.

Fill each base with cold pastry cream, mound slightly in center. Roll out remaining dough discs for lids, place over filling, press edges to seal. Brush tops with beaten egg white, and bake for about 30 minutes until deep golden.

Let pasticciotti cool enough to handle before removing from molds. Best served fresh, but can be kept airtight for up to 1 day.