Chicken Pot Pie with Homemade Puff Pastry

Instructions

1. Make Puff Pastry Dough: In a large bowl, mix 2 cups flour and 1 tsp fine sea salt. Grate 2 cups cold butter (previously chilled) and add to flour. Mix lightly with a fork to combine, handling dough as little as possible. Gradually add about 10 tbsp cold water just until dough comes together. Knead lightly, cover with plastic wrap, and refrigerate for 20 minutes.
2. Laminate Dough with Folds: Lightly flour work surface and roll dough into a rough rectangle. Perform envelope folds by folding one side two-thirds over, then the last third over that. Roll out again into a rectangle and repeat folding. Perform a total of 5 folds. Wrap dough in plastic wrap and refrigerate for 1 hour.
3. Cook Chicken: Heat a cast iron pan over medium heat with a couple tablespoons of oil. Season 2 chicken breasts with salt and sear until golden on both sides. Transfer pan to a 400°F (204°C) oven and cook chicken until internal temperature reaches 165°F (74°C). Remove and let rest.
4. Prepare Vegetables: Peel pearl onions by cutting off the root and peeling. Halve larger onions, leaving small ones whole to hold together. Peel and chop celery root into 1/4 to 1/2 inch cubes to make about 1 cup. Peel and chop baby carrots into similar size pieces to yield about 2 cups. Mince 3 cloves of garlic.
5. Cook Filling: In the same cast iron pan with chicken juices, add 2 tbsp butter and a little oil. Add pearl onions and cook until lightly colored. Add celery root and cook 1-2 minutes, then add carrots. Season with kosher salt and pepper. Cook for about 10 minutes until vegetables soften. Add garlic and cook for 1 minute.
6. Make Sauce and Combine Filling: Sprinkle 4 tbsp flour over vegetables and cook off the raw taste. Slowly add 2 cups chicken stock, stirring until sauce thickens and comes to a boil. Add sliced chicken (cut into 1/4 inch cubes or shredded), 1 cup frozen peas, and stir. Remove from heat and stir in 2/3 cup cream, chopped parsley, and a few sprigs of tarragon. Add 1 cup grated cheese and adjust salt to taste. Let filling cool.
7. Assemble Pot Pie: Flour work surface and roll puff pastry into a rough circle about the size of the cast iron pan. Place cooled filling into the pan and cover with puff pastry. Roll and crimp edges to seal. Brush pastry with egg yolk.
8. Bake: Bake in a 400°F (204°C) oven for about 40 minutes until pastry is golden brown and cooked through. Place a baking tray underneath to catch any overflow.