Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper. In a small bowl, whisk the egg with the half and half to make an egg wash.
1 egg, 1 tablespoon half and half
On a lightly floured surface, cut the thawed puff pastry into 3–4 inch circles with a biscuit or cookie cutter. Use a smaller cutter to cut the centers out of half the circles to create pastry rings.
2 puff pastry sheets
Place the whole circles on the prepared baking sheet. Brush the tops with egg wash (avoid the sides), then stack a pastry ring on top of each circle to form a shell. Brush the tops with more egg wash.
Bake for 15 minutes, until puffed and golden. Remove from the oven and gently press down the centers with the back of a spoon to make room for the filling.
While the pastry bakes, season the chicken with salt and pepper. Heat the butter and olive oil in a large skillet over medium-high heat. Add the chicken and cook until golden brown and just cooked through, 8-10 minutes. Transfer to a plate.
4 boneless skinless chicken thighs, 2 tablespoon unsalted butter, 1 tablespoon olive oil
Add the mushrooms and onion to the skillet with a pinch of salt. Cook until softened and browned, about 6–7 minutes. Stir in the garlic and cook for 30 seconds, until fragrant.
8 oz cremini mushrooms, 1 small onion, 3 cloves garlic
Pour in the brandy, scraping up the browned bits from the bottom of the pan. Let it simmer for 1–2 minutes to cook off the alcohol.
½ cup brandy
Sprinkle the flour over the vegetables and stir to coat. Cook for 1 minute, then gradually whisk in the chicken stock until smooth. Stir in the cream, season with nutmeg, salt, and pepper, and simmer for 4–5 minutes until the sauce thickens slightly.
3 tablespoon all-purpose flour, 2 cups chicken stock, 1 cup heavy cream, ⅛ teaspoon nutmeg
Return the chicken to the skillet. Add the green beans and simmer for 15 minutes, until the beans are tender and the filling is heated through. Add pimentos and peas at the last 5 minutes of cooking. Taste and adjust seasoning as needed.
1 cup green beans, 1 cup frozen peas, ½ cup pimientos, Kosher salt & freshly ground black pepper
Spoon the hot filling into the baked puff pastry shells. Garnish with parsley or chives and serve immediately so the pastry stays crisp.
2 tablespoon fresh parsley or chives