Vanilla Bean Crème Brûlée Tart

Crème brûlée is routinely baked in ramekins in a water bath. Since a tart shell cannot sit surrounded by water, the method I use here, adapted from a recipe in Desserts by Nancy Silverton, is to blind-bake the tart shell, then cook the custard separately over boiling water. This requires prolonged rapid whisking to foam the egg yolks while keeping them from curdling. The custard is then ladled into th