- For the crust:
- 1 cup all-purpose flour
- 3⁄4 teaspoon kosher salt, plus more to taste
- 1 teaspoon whole black peppercorns, ground in a mortar with a pestle
- 6 tablespoons butter, chilled and cut into cubes
- 1⁄4 cup ice water
- For the filling:
- 4 to 5 medium-sized, dense-fleshed heirloom tomatoes, such as Northern Lights or Brandywine
- 4 strips bacon or pancetta
- 3 ounces Italian fontina, thinly sliced
First, make the galette dough. Combine the flour, kosher salt, and ground black peppercorns in a small work bowl, and use your fingers or a pastry cutter to work in the butter so that the mixture resembles coarse-ground cornmeal. Add the ice water, gently press the dough together, and gather it up into a ball. Chill for 1 hour.
Meanwhile, remove the stem cores of each tomato and slice off each end. Cut each tomato into 3/8-inch-thick round slices, season with salt, cover the slices with a tea towel, and set them aside. Fry the pancetta or bacon until it is just barely crisp; transfer to absorbent paper and set aside. Drain the juices that have collected around the tomatoes, using your fingers to press out any large pockets of seeds and gel.
Preheat the oven to 400°F. Line a baking sheet with parchment paper and set it aside. Set the chilled dough on a floured work surface and use the palm of your hand to pat it flat. Roll it into a 14-inch circle about 1/8-inch thick and carefully transfer it to the parchment-lined baking sheet.
Arrange the cheese over the surface of the tart, leaving a 2-inch margin around the edges. If more juices have accumulated around the tomatoes, drain them again and place the tomatoes on top of the cheese in concentric circles that overlap slightly. Season the tomatoes lightly with kosher salt and generously with black pepper from the mill. Scatter the chives over the top of the tomatoes, arrange the bacon strips on top, and then gently fold the edges of the tart up and over the tomatoes, pleating the edges as you fold them. Using a pastry brush, brush the edge of the tart lightly with the egg wash and sprinkle it with the coarse or Hawaiian salt. Bake until the pastry is golden brown and the tomatoes soft and fragrant, about 35 to 40 minutes. Transfer to a rack to cool, cut into wedges, and serve warm.