Heat a large Dutch oven or heavy-bottom saucepan over low heat, then add 1 tablespoon of the butter. Add the mushrooms along with a pinch of salt and cook for 3-4 minutes, stirring periodically, to soften and release some of their natural liquid. Turn the heat up to medium and brown the mushrooms for several minutes. Remove the mushrooms from the pan, set aside, and turn the heat down to medium-low.
Melt the remaining butter and add the onions, celery and carrots. Cook for 5-7 minutes until soft, stirring periodically, then add the garlic and cook for an additional minute. Stir in the flour and cook for 3-4 minutes, stirring frequently. Add the brandy, stock, paprika, and cooked mushrooms.
Bring to a simmer and allow the sauce to thicken, stirring periodically, for 3-5 minutes. Stir in the heavy cream and remove from the heat. Add the truffle oil (if using), thyme, parsley, salt and pepper. Taste; add more seasoning if desired.
Preheat the oven to 425 degrees F. Divide the filling into four 8-ounce ramekins (approximately 4x2 inches) and place on a baking sheet.
On a lightly floured surface, roll the puff pastry thin and cut 4 rounds approximately 1/2 - 1 inch larger than the width of the ramekins. Brush egg wash on the rim of each ramekin and 1/2 inch down the sides. Top with the puff pastry, folding the excess over and gently pressing it against the ramekins (a fork can also be lightly pressed against the puff to help seal it to the dish). Brush the top of the dough with egg wash and use a small knife to poke 3 small holes in the top of each pot pie.
Bake for 20-25 minutes, or until the tops are golden brown. Allow to cool briefly before serving.
I’ve used crimini mushrooms, but any variety will work in this recipe. Shiitakes, portobellos, oysters, button mushrooms… you can also try using a mix. If you don't consume alcohol, the brandy can be omitted from the recipe.