Preheat oven to 350°F. In a medium saucepan, cover potato slices with water by two inches. Simmer, uncovered, until tender, about 10 minutes. Drain. If the potatoes don’t seem very dry, pat them dry with towels.
Arrange potato slices, overlapping slightly, in concentric circles around the tart pan. Sprinkle blue cheese over potatoes. Whisk cream and egg yolk together and pour into tart shell, then sprinkle tart with herbs of your choice and salt.
Bake tart on a baking sheet until bubbling and golden brown, about 45 to 50 minutes. Cool in pan on rack and serve warm or cold. With a big green salad, for balance.