Step 1

Preheat the oven to 400 degrees.

Step 2

Melt 2 tablespoons of butter in a 10-inch cast-iron skillet over medium-high heat. Add the mushrooms and let sit for 3 minutes, without stirring. Reduce the heat to medium and add the garlic and thyme. Let cook 2 more minutes, stirring frequently, until the mushrooms are tender. Remove to a plate and set aside.

Step 3

Return the skillet to medium heat and add the remaining 3 tablespoons of butter. Once melted, add the carrots, onion, celery and salt and pepper. Let cook 7 minutes, stirring occasionally, until slightly tender. Add the flour and stir well to combine. Cook 2 more minutes. Add the vegetable stock and increase the heat to medium-high. Cook 5-7 minutes, stirring frequently, until the mixture reaches a low boil and thickens. Pour in ½ cup of heavy cream, white beans, ½ cup of grated parmesan cheese and the reserved mushrooms. Stir well to combine, season with salt and pepper, if desired, and remove from the heat.

Step 4

Carefully transfer the skillet to a sheet tray lined with foil. Unfold the puff pastry and carefully place it in the center of the skillet over top of the pot pie filling (draping over the edges of the skillet). Brush the pastry all over with the remaining 1 tablespoon of heavy cream. Sprinkle with extra parmesan cheese, thyme leaves and black pepper.

Step 5

Bake for 20-25 minutes until the top crust is golden brown and the mixture is bubbly.  Let rest 5 minutes, then scoop into bowls and serve.