How to Make It
Preheat oven to 425°F. Heat oil in a Dutch oven over medium-high. Add mushrooms, onion, and celery; cook, stirring often, until softened, 7 to 8 minutes. Add sweet potato and thyme; cook until tender and liquid has evaporated, 6 to 7 minutes. Stir in flour to coat. Add stock and milk; bring to a boil, stirring constantly. Boil 1 minute. Remove from heat; stir in chicken, lima beans, and salt. Let cool 20 minutes.
Cut puff pastry into 4 (4 1/4-inch) rounds. Place 4 (10-ounce) ramekins on a baking sheet; fill with chicken mixture. Top with dough rounds; bake at 425°F until golden brown, 17 to 19 minutes. Garnish with thyme.