Directions

• Make the filling:
• Unravel the pancetta so that it is one, long strip. (You may have to do some cutting to get it unraveled and evenly thick.) Slice it into 1/16-inch-thick pieces. Measure out 3.5 oz. (approx. 1/2-cup) and set aside. Repurpose the rest.
• Pre-heat a 10-inch cast iron skillet over a medium-high flame (setting 6 of 9). Heat the oil and butter in a saucepan, gently swirling the pan once or twice, until the butter has melted. Wait about 20 seconds, then add the pacetta and the diced chicken thighs and fry, turning occasionally, for 5–8 minutes, until the chicken has taken on some golden color. Reserve 1 Tbs of the greens from the sping onions. Add the rest of them, along with the leek, to the pan, and fry until softened, 5 minutes. Add the garlic and mushrooms and cook for until softened, 2–3 minutes.
• Sprinkle on the flour and stir to ensure the meat and vegetables are well coated. Cook, stirring constantly, 1 minute. Add the chicken stock. It should immediatly begin to boil. Use a wooden spatula to help the stock deglaze the pan. Once the pan is deglazed (or close to it), off heat. The mixture should be wet, but not saucy. Continue to scrape the bottom of the pan with the spatula for a minute or two, to ensure that nothing sticks.
• Add the crème fraîche and herbs, then season the filling with salt and pepper. Transfer to a bowl and refrigerate until completely cool. (While you make and chill the pastry should be long enough).
• Make the pastry:
• Place the flour and salt in a food processor. Process for 10 seconds. Add a cube of butter, and give the machine 2 one-second pulses. Add a new cube and pulse again for 2 one-second pulses. Continue until you’ve added all the cubes. Run the machine until the mixture resembles fine breadcrumbs. With the machine running, add 1 Tablespoon of water at a time, just until the mixture comes together to a dough. Tip the dough onto a lightly floured work surface, bring it together into a ball, then flatten it to a disk. Wrap it and chill it for 15 minutes.
• Make the pies:
• Butter 4 one-cup ramekins generously; set aside. Remove the pastry from the fridge. Set aside 1/3 of the dough. Divide the remainder into 4 equal portions. Roll out 1 of the 4 portions on a lightly floured work surface until 1/8-inch thick. Cut the dough into a 7-inch circle and discard (or repurpose) excess. Fit the dough circle snugly into one of the prepared ramekins. Mold to ensure an even thickness all around, coming straight up out of the ramekin like a collar, at least 1/4-inch. Continue until all ramekins have dough.
• Pre-heat oven to 400°F (375°F convection). Divide the cooled filling between the ramekins, pressing it down well.
• Divide reserved pastry into 4 equal portions. Roll out 1 of the 4 portions on a lightly floured work surface to 1/8-inch thick. Using a 4-inch round cutter, cut out a pastry lid. Place lid on top of one of the filled cases, pressing its edges together with the pastry collar to seal and make a pie. Crimp without allowing the crimp to overhang the ramekin. Poke 1 or 2 vent holes into the pie. Repeat for remaining pies. Brush the tops with the egg, being careful to avoid applying too much egg directly onto the seam where the pastry meets the ramekin.
• Bake the pies on a tray until the pastry is crisp and golden, 25 minutes. Cool on a rack. As soon as the pies are cool enough to handle, run a cake release tool around the edge where the pastry meets the ramekin, being careful not to poke the tool into the pie. Invert, and gently shake the pie out of its ramekin. Allow to cool completely on rack. Serve cold, or at room temperature, with sauce on the side.
• Make the crème fraîche dijon sauce:
• Stir together all ingredients. (See notes)