Directions

1. Preheat oven to 350°F.
2. In a 1 quart bowl combine the eggs and heavy cream. Whisk until smooth.
3. Arrange the baked tart shells on a baking sheet and divide the onions and walnuts evenly among them.
4. Crumble the blue cheese evenly among the shells.
5. Divide the custard evenly among the shells, filling to the top.
6. Bake the tarts until puffed and golden brown, about 20 minutes, rotating baking sheet after 10 minutes if browning unevenly.
7. Let tarts cool to room temperature and cut into quarters or sixths. Arrange on serving tray.
8. Tart shells may be baked and stored covered at room temperature up to 3 days. Custard may be made ahead and refrigerated covered for 3 days. Tarts are best served the day they are made. Refrigerate leftovers and serve chilled.