For Dough: Preheat oven to 350 degrees. Combine the flour, cornmeal and salt in a bowl or a standing mixer with a paddle attachment. Add butter and combine until butter starts to break down into small pieces. Slowly add the ice water that is combined with the vinegar. Dough should come together and form a ball. Roll the dough about 1/8” thick and Line a tart shell. Refrigerate the tart shell for 20-30 min. Line the tart shell with foil and place ceramic or metal weights in the middle of the tart. Par bake the shell for 25 minutes. Remove the tart from the oven and allow for the shell to cool then remove the foil and weights.
For Mushrooms: In a medium size saute pan, heat oil on low heat. Add minced shallots. Season with salt. Add mushrooms and fresh thyme and cook covered for about 20 minutes until mushrooms have exuded liquid. Remove lid and continue to cook until almost all liquid has been evaporated. Add garlic (if using) during last 5 minutes of cooking. Cool mushrooms and then finely chop or pulse in a robot coupe
For Custard: Whisk together the eggs, crème fraiche, salt, black pepper and fresh thyme. Fold in the grated mushrooms and grated cheese. Fill the par baked tart shell until almost completely full. Bake for additional 25 minutes at 350 degrees until golden brown.
Take a look at our recommended pairings below.