1 1/2cupsrotisserie chicken meat,torn into bite-size pieces
1sheet frozen puff pastry,such as Dufour or Pepperidge Farm, thawed
Place a rack in upper third of oven; preheat to 425°. Heat oil in an 8-inch cast-iron or other heavy ovenproof skillet over medium-high heat. Add onions; cook, stirring occasionally, until beginning to brown, about 4 minutes.
Reduce heat to medium-low. Add garlic and sage to skillet and cook, stirring occasionally, until garlic begins to brown, about 2 minutes.
Add 1/2 of vegetables and season with salt and pepper. Cook, stirring constantly, for 4 minutes. Remove from pan then cook the other half of the vegetables, adding any leafy greens at the end of cooking and cook those until wilted. Place al vegetables back into the pan
Sprinkle flour over, and stir well to combine.
Stir in broth, 1/2-cupful at a time, then add milk. Bring to a boil, reduce heat, and simmer until vegetables are softened and broth is thickened, 8-10 minutes. Add chicken to skillet, stir, and season with salt and pepper.
Unfold puff pastry and smooth any creases using a rolling pin; place over skillet, allowing corners to hang over sides. Whisk egg and 1 teaspoon water in a small bowl. Brush pastry with egg wash; cut four 1-inch slits in top to vent.
Bake pot pie until pastry is beginning to brown, 15-20 minutes. Reduce oven temperature to 375° and bake until pastry is deep golden brown and crisp, 15-20 minutes longer. Let cool for 10 minutes before serving.
Use whatever vegetables you have on hand. If you're using greens, use one bunch for 1 cup of the vegetables in the recipe.