8 ounces cremini mushrooms, stems trimmed and halved if large
4 carrots, cut into 1-inch pieces
1 medium onion, chopped
1/3 cup all-purpose flour
2 sprigs fresh thyme
1 bay leaf
1 1/2 pounds boneless, skinless chicken thighs (about 8)
kosher salt and black pepper
1 sheet puff pastry (half a 17.3-ounce package), thawed
1 cup frozen peas
1 cup frozen green beans
1/3 cup heavy cream
In a 4- to 6-quart slow cooker, mix together the mushrooms, carrots, onion, flour, thyme, bay leaf, and ½ cup water. Place the chicken on top; season with 1 teaspoon salt and ¼ teaspoon pepper.
Cover and cook until the chicken and vegetables are tender, on low for 7 to 8 hours or on high for 4 to 5 hours (this will shorten total recipe time).
Thirty minutes before serving, heat oven to 425° F. Using a 4½-inch cutter or large glass, cut the pastry into 4 circles. Place on a baking sheet and bake until golden, 8 to 10 minutes.
Ten minutes before serving, add the peas, green beans, cream, and ½ teaspoon salt to the chicken mixture and stir to combine. Cover and cook on high or low until heated through, 5 to 10 minutes more. To serve, place the chicken mixture in bowls and top with the pastry rounds.