• Preheat the oven to 375°F. Grease a 9-inch deep pie dish and set it aside.

For the crust

• In a bowl, toss together the flour, salt, shredded cheddar cheese, Parmesan cheese, and thyme. Add the cubes of cold butter and toss them with the dry ingredients. Using thumbs and forefingers, work the butter into the flour until it resembles wet sand with pieces of butter no larger than the size of a pea. Add cold water, starting with 4 tbsp. Toss to combine and add more water 1 tbsp at a time to create a cohesive dough that holds together when making a fist of the crumbs. Press the dough into a smooth disk. Wrap tightly and chill in the refrigerator for 20-25 mintues.
  1 ½ cups all-purpose flour, ½ tsp kosher salt, 1 cup shredded cheddar cheese, ½ cup grated Parmesan cheese, 2 tsp fresh thyme leaves, 10 tbsp (1 ¼ sticks) unsalted butter, 4-6 tbsp ice cold water

For the filling

• Cube the chicken into ½-inch pieces. Season with the salt and pepper evenly, and set aside to cook vegetables, or set in the refrigerator to season for up to 30 minutes.
  1 lb boneless and skinless chicken thighs, ¾ tsp kosher salt, ½ tsp freshly ground black pepper
• Melt the butter in a large 12-inch skillet or shallow stockpot. Once melted, add the onion, carrots, and celery. Season with a sprinkling of kosher salt and sauté until the onions are translucent, 4-6 minutes. Add the prepared chicken and sauté until it is fully cooked, 8-10 minutes.
  3 tbsp unsalted butter, 2 carrots, 1 onion, 1 stalk celery
• Pour in the white wine and bring it to a simmer. Cook until the wine is mostly evaporated, 3-4 minutes. Add the thyme and sage, stir, and sprinkle in the flour. Stir and cook the flour until it forms a paste-like coating, 2 minutes. While stirring, slowly pour in the stock. Once added, continue to stir and cook until the liquid is thickened, 4-6 minutes. Remove from the heat and add the peas and pearl onions. Stir and set the filling side.
  ½ cup white wine, 1 tbsp minced fresh sage, 2 tsp minced fresh thyme, ¼ cup all-purpose flour, 2 cups chicken stock, 1 cup frozen peas, 1 cup frozen pearl onions
• On a lightly floured surface, roll the chilled crust out to an 11-inch circle. Pour the filling into the prepared deep pie dish and place the rolled crust on top, allowing the excess to hang over the edge. Cut off the excess with the rim of the pie dish. Place the dish on a parchment-lined baking sheet. Brush the top with an egg wash and place in the preheated 375°F oven. Bake until the crust is golden brown and the filling is warmed through, 30-35 minutes. Remove and allow the pie to cool for 10 minutes before serving.