Scottish Chicken Pie from Egg & Chicken by Grant MacPherson

Ingredients

• 1 cup fresh or frozen peas
• 1 cup sliced mushrooms
• 1 teaspoon minced fresh thyme leaves
• 1 tablespoon chopped fresh curly or flat-leaf parsley
• 1 medium yellow onion, chopped
• 1 cup peeled and chopped carrots
• 1 cup chopped celery
• 4 tablespoons unsalted butter
• ¼ cup all-purpose flour
• 3 cups Chicken Stock, or good quality store-bought chicken broth
• 2 tablespoons grapeseed oil (or other neutral oil), divided
• Kosher salt and freshly ground black pepper
• 2 skinless, boneless chicken breasts
• 2 egg yolks, beaten
• 4 tablespoons ice water
• 1 stick unsalted butter, cubed
• Pinch kosher salt
• 1 teaspoon sugar
• 1 ¼ cups all-purpose flour