6ounces1 1/2 sticks chilled butter, cut into 1/2-inch bits
2tablespoonspacked blue cheese
1/3cupcold wateror more as needed
2poundsyellow onionssliced very thinly
1herb bouquet of 2 - 3 bunches of fresh thyme tied in cheesecloth
1clovegarlicpeeled and smashed
1red bell pepper
1tablespooncapers plus 1 teaspoon of the brining liquid
10niçoise olivespitted, halved (kalamata olives work just fine)
Place the flour, salt, and sugar in the bowl of a food processor. Add the butter and blue cheese all at once and pulse until the butter is the size of peas. Do not overdo this step as the fat will be blended more thoroughly later.
Add the water and pulse 10 - 12 times until the mixture starts to come together as a dough. It will still be very crumbly.
Spill it out onto a lightly floured workspace, and press and slide the heel of your hand through the mixture 3 times. This technique is called fraisage, and effectively creates layers of fat that translate into a beautiful flakey crust.
Form the dough into a single large disk and wrap it in wax paper. Chill in the refrigerator for one hour, or until firm.
Preheat the oven to 400 degrees F. Roll out the dough as quickly as possible due to it's high butter content. I posted tips with photos for rolling out dough here.
Fold the rolled out dough in half, and in half again, and carefully place in the base of a tart pan with a removable bottom. Gently tuck the dough into the fluted edges, allowing the dough to be 1/2" above the sides of the tart pan. The dough will have some shrinkage.
Line the tart with parchment paper and pie weights. Bake for 8 - 9 minutes at sea level, 12 minutes at 6500 feet above sea level, or until the edges of the pâte brisée begin to set up. Remove the pie weights and the parchment paper, prick the bottom of the shell with a fork to keep the dough from rising, and continue to bake for 2 - 3 minutes at sea level, 5 minutes at 6500 feet above sea level. When the shell is starting to brown, remove it from the oven. Set aside while you prepare the Pissaladiére Niçoise.
Cook the onions very slowly in the olive oil with the herb bouquet, smashed garlic, and salt for about one hour, or until a golden brown and very tender. Discard the herb bouquest. Stir in the cloves and pepper, and adjust for seasoning. Remove from the heat and add the balsamic vinegar, scraping up any bits of onion that have cooked onto the bottom of the pan. There's a lot of flavor there!
Spread the onions evenly on the bottom of the Pâte Brisèe.
Preheat the oven to 425 degrees F. Slice the red pepper into long thin slices, toss with a little olive oil, and roast for 15 minutes. Add the capers and brine and continue to roast for another 15 minutes.
Arrange the pepper strips on top of the onions in a pattern. Sprinkle the capers on top.
Arrange the olives in a pattern on the tart.
Reduce the oven temperature to 400 degrees F. Return the tart to the oven and bake for 10 to 15 minutes at sea level, 20 minutes at 6500 feet above sea level, or until bubbling hot.