PREHEAT OVEN AND PREP PUFF PASTRY: Preheat your oven to 400°F. Unfold the puff pastry and let it rest on the counter until slightly softened and easier to cut.

SWEAT THE VEGETABLES: In a large stockpot, melt 4 tablespoons (½ stick) unsalted butter over medium heat. Add 1 small yellow onion, 3 medium carrots, 3 ribs celery, and 1 large Russet potato. Add half of the salt. Sauté for 3 to 4 minutes, until the onion turns translucent and the vegetables begin to soften. You should smell the sweetness of the vegetables as they warm.

ADD FLOUR, PEPPER, REMAINING SALT, AND HERBS: Sprinkle in 4 tablespoons all purpose flour, ½ teaspoon fresh ground black pepper, the remaining salt, 1 teaspoon chopped rosemary, 2 teaspoons chopped thyme, and 1 tablespoon chopped parsley. Cook for 2 to 3 minutes, stirring often. The mixture will thicken and smell warm and nutty as the flour toasts.

ADD LIQUIDS AND CHICKEN: Pour in 1 ½ cups whole milk, 1 ½ cups chicken stock, and ½ cup heavy cream. Stir well, scraping the bottom of the pot. Add ½ cup frozen peas and 2 cups diced cooked chicken. Increase heat until the mixture begins a gentle simmer.

SIMMER UNTIL THICKENED: Simmer for 5 to 10 minutes, stirring occasionally, until the vegetables are tender and the filling thickens into a creamy gravy. Drag a spoon across the bottom of the pot; the trail should slowly close. Taste and add a pinch more kosher salt if needed.

CUT PASTRY TOPS: Place an oven safe bowl upside down on the puff pastry to measure. Cut circles about ½ to ¾ inch larger than the bowl so the pastry can drape and puff.

ASSEMBLE POT PIES: Spoon the hot filling into oven safe bowls. Lay a pastry round over each bowl and gently press around the rim to seal. If the pastry is thick, cut one small steam vent in the top.

BRUSH WITH EGG WASH: Whisk 1 large egg with 1 tablespoon water. Brush a thin, even layer over each pastry top.

BAKE: Bake for 15 minutes, until the crust is puffed and a deep golden brown. Loosely cover with foil and continue baking for 15 minutes longer, until the filling bubbles gently around the edges.

REST AND SERVE: Let the pot pies cool for 5 minutes before serving. The filling will be very hot and will thicken slightly as it rests.