The purple/blue potatoes make this tart visually striking, but the real star is the bluefoot mushrooms. Bluefoot mushrooms are hard to find, whether you are foraging in a forest, or picking through high end grocers. But the result is well worth the hunting. Intensely woody, rich and meaty the cooked bluefoots give off an intoxicating, swoon-enducing aroma. Not unlike porcini, but with a character that is distinctly their own. Bluefoots tend to be very clean (just brush off any dirt around the stem). They do best when they are given a long cooking time, and pair well with members of the onion family and cream; rather like truffles.
So I started knowing I wanted to make a bluefoot and blue potato tart. Add cream and shallots to bring out the bluefoot’s flavor, but it still needed something else. I hesitated before adding blue cheese. The flavor is incredible, but it can tend to overwhelm. But I remembered a gorgonzola risotto I enjoyed– the cheese was mixed into a cream sauce which rendered its flavor surprisingly and pleasantly mild. So I thought a moderate dose of blue cheese might just do the trick. I love the flavor combination of the woody mushrooms in contrast with the tangy funky blue cheese. The blueness of these elements certainly brought them together, but given the whole spectrum, I wouldn’t change a thing about this combination. The decadent cream, cheese and expensive bluefoots make this a dish to be enjoyed once in a blue moon, so I thought the name was apropos in more than one way.
1 tart shell, rolled and chilled (see my recipe for flaky pie dough)
1 ¼ lb purple potatoes
3-4 T crumbled blue cheese
2 T. butter
5-6 bluefoot mushrooms
½ c. heavy cream
1 t. salt
Preheat oven to 375°F. Half fill a large stock pot and place over high heat. Scrub potatoes and cut into ¼“ slices. Once the water has come to a boil, add potatoes and cook for 4-5 minutes, until tender. Remove potatoes and drain in a colander.
Peel and finely chop shallots. Delicately clean off any dirt from the mushrooms with a moist paper towel. Slice into ¼” thick slices. Place a sauté pan over medium heat and add butter. Add shallots and cook until translucent. Add in mushrooms and cook for 5-6 minutes, stirring intermittently, until the surface of the mushrooms is lightly browned and the mushrooms are tender. . Add in cream. Cover reduce heat to low, and let mushrooms simmer in cream for 10-15 minutes. Remove pan from heat and stir in salt.
Let the mushroom and cream mixture cool for a few minutes, then stir in the egg and 2 T blue cheese. Reserve a few attractive mushroom slices for the top of the tart. Pour into your prebaked tart shell. Arrange the potato slices into a spiral, switching the direction of the spiral each row. Place the mushroom slices in the center and scatter remaining blue cheese over the surface of the tart.
Bake tart for 45-55 minutes, until the crust is golden and the custard is set.
This tart is best served warm.