Preheat oven to 400°F (200°C).
Optional bottom crust: Fit one puff pastry sheet into a 9x13-inch pan, pressing up the sides. Prick all over with a fork and bake 12–15 minutes until lightly golden. Cool while preparing filling.
In a large pan, cook bacon until crispy; remove and reserve 2–3 Tbsp grease.
Sauté onion in grease until softened (5 min). Add garlic (1–2 min), then carrots (7–10 min).
Stir in flour and cook 2 min. Whisk in dissolved bouillon (3 tsp in 2 cups water) and cream; simmer until slightly thickened.
Stir in thyme, rosemary, bacon, chicken, peas, salt, and pepper. Simmer a few minutes, then remove from heat.
Transfer filling to baking dish. Top with puff pastry squares, overlapping slightly. Brush with beaten egg.
Bake 30–35 min, until pastry is golden and crisp. Rest 10 min before serving.
