Preheat oven to 375°F. Generously grease 2-½ inch mini tart pans or 16 wells in two 12-well muffin tins.
Roll out pie dough and cut into 16 (3-½ inch) rounds. Press pastry into prepared pans.
Whisk together the cream, eggs, Traditional Pub Mustard, salt, pepper, and nutmeg.
Divide tomatoes, basil, and cheese evenly in crusts.
Fill each tart pan ¾ full with egg custard. If using individual tart pans, place them on a baking sheet.
Bake for 10-15 minutes or until the center of each tart is firm. Allow to cool 5 minutes, then remove from pans. (You may have to run a small knife around the pan to loosen the crust.)
Tarts can be frozen for 1-2 weeks if stored in an airtight container. Otherwise serve immediately.