The tart dough can be frozen for up to 1 month. The pastry cream can be refrigerated, covered, overnight. Bring the dough and pastry cream to room temperature before using.
pure lemon oil, cold-pressed from lemon rinds, is available at specialty-food shops and online at boyajianinc.com.
Excess dough can be made into cookies: Roll the dough out to a 1/4-inch thickness. using a sharp knife, cut the dough into 3-inch squares. Brush the squares with egg wash, score them with a fork and bake for 20 minutes in a 350° oven until golden.
For a sweet, fragrant dessert wine to match, Daniel Johnnes prefers Muscats from the south of France, such as a Muscat de Rivesaltes or the generally more delicate Muscat de Beaumes-de-Venise.