Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper. Cut thawed puff pastry into 6 rounds using a cookie cutter or mason jar ring (or cut into squares). Place on the baking sheet, brush lightly with beaten egg wash, and sprinkle with a pinch of flaky sea salt and dried thyme. Bake for 12 to 15 minutes until deeply golden brown and puffed. Set aside.

While pastry bakes, melt butter in a large Dutch oven or heavy soup pot over medium heat. Add the diced onion, sliced carrots, and diced celery. Sauté for 5 to 6 minutes until the vegetables begin to soften and become fragrant. Stir in minced garlic, fresh thyme, and rosemary; cook for 1 more minute until aromatic.

Sprinkle the flour evenly over the sautéed vegetables. Stir continuously for 1 to 2 minutes to cook out the raw flour taste. Slowly pour in the chicken broth in a steady stream while whisking vigorously to dissolve the flour and prevent any lumps.

Bring the broth to a gentle simmer over medium-high heat. Reduce heat to medium-low and let it simmer uncovered for 8 to 10 minutes until the carrots are fork-tender and the soup has thickened to a velvety, coat-the-back-of-a-spoon consistency.

Stir in the shredded cooked chicken, heavy cream, frozen peas, and sweet corn. Simmer gently for another 3 to 4 minutes until everything is steaming hot and heated through. Season with kosher salt and black pepper to taste.

Ladle hot creamy pot pie soup into wide serving bowls. Float a warm, freshly baked golden puff pastry biscuit directly on top of each bowl. Garnish with cracked black pepper and fresh thyme sprigs, and serve immediately!