Preheat the oven to 375 degrees F. Set the chicken in a small roasting pan; season with 3/4 teaspoon salt, and pepper to taste. Roast until golden and cooked through, about 40 minutes; let cool. Shred the meat, discarding the skin and bones.
Meanwhile, heat the olive oil in a large skillet over medium heat. Add the sliced leeks and fennel and sprinkle with 1/4 teaspoon salt. Cook, stirring occasionally, until the vegetables soften, about 8 minutes. Sprinkle in the flour; cook, stirring, 1 minute. Add the Pernod and saffron; simmer until the liquid is almost evaporated, about 1 more minute.
Add 3/4 cup water, the heavy cream, orange zest, potatoes and 1/2 teaspoon salt to the skillet. Bring to a simmer over medium-high heat and cook until the potatoes are almost tender, 8 to 10 minutes. Stir in the shredded chicken, tomatoes and fennel fronds; season with salt and pepper.
Preheat the oven to 350 degrees F. Set out six 8-to-10-ounce ramekins. Unfold the puff pastry on a lightly floured surface. Gently roll out the pastry so it is extended by about 1/2 inch in each direction. Using a ramekin as a guide, cut out 6 rounds slightly larger than the ramekins with a paring knife.
Divide the filling among the ramekins, filling each nearly to the top. Brush the rim and outer edge of 1 ramekin with the beaten egg. Set a puff pastry round on top and gently press around the edge to secure the dough. Repeat. Brush the remaining egg over the pastry.
Transfer the potpies to a baking sheet and bake until the pastry is domed and golden brown, about 30 minutes. Let stand 5 minutes before serving.