Mushroom Puff Pastry Tarts with Creme Fraiche, Gruyère, and Thyme

as some of you know, i work part-time at a neighborhood bakery, and while i don’t do any of the baking or prepwork, i still learn a few things here and there. one of my favorite things from the shop is a savory puff pastry tart that’s filled with prosciutto and eggs — i love that we can take a premade puff pastry shet and turn it into something that looks fancy with a few cuts and folds. i borrowed from the technique for this recipe but filled them with a savory, umami-filled mushroom filling. i don’t know if anyone remembers the mushroom turnovers from the trader joe’s freezer aisle, but these remind me of those!

can i use fresh mushrooms instead of dried?

yes — fresh mushrooms would also work in these puff pastry tarts! the main differences come down to amount, flavor, and texture.

• amount: dried mushrooms expand to nearly three times their size once rehydrated. my recipe calls for 1 ½ cups dried mushrooms, which equals about 4–5 cups of fresh, sliced mushrooms
• flavor: dried mushrooms (especially porcini) bring an earthy, almost smoky intensity. fresh mushrooms are lighter and more delicate. to build more depth, cook them until deeply golden and consider adding a splash of soy sauce, sherry, or even a spoonful of miso to mimic the umami boost you’d normally get from the mushroom soaking liquid
• texture: rehydrated mushrooms are slightly chewy, while fresh mushrooms start out tender but release a lot of water as they cook. make sure you sauté fresh mushrooms long enough for the liquid to fully evaporate before stirring in the crème fraîche. this step keeps your puff pastry crisp instead of soggy

i used (makes 4):

• one sheet of puff pastry , defrosted
• 1.5 cups dehydrated mixed mushrooms, rehydrated (i use this one from costco)
• 1/4 yellow onion, thinly sliced
• 2 cloves garlic, sliced
• 2 tbsp creme fraiche
• 1 large sprig of thyme
• 1 tbsp unsalted butter
• 1-2 tbsp gruyere, grated
• salt
• pepper
• 1 egg, beaten
• garnish: additional creme fraiche, thyme

to make mushroom puff pastry tarts:

• melt butter in a skillet over medium-low heat, add onion and a pinch of salt and cook until soft and translucent, ~7-10 minutes
• stir in garlic, thyme, and rehydrated mushrooms. cook until most of the moisture has evaporated ~5-7 minutes
• season with salt and black pepper, then remove from heat. once cooled, stir in creme fraiche and let it continue to cool to room temperature
• unfold the puff pastry sheet, if not already a square shape, gently roll out into a square using a rolling pin. then, divide sheet into 4 squares about 4–5 inches wide. fold each square diagonally into a triangle, then use a sharp knife to cut a ½-inch border along the two outer edges (see photo) — stopping just before the corners so the cuts don’t meet. unfold the square again, then gently take one cut corner and loop it across to the opposite side, repeating with the other corner. this creates a twisted frame effect that bakes up into a pretty, layered border (see photos above)
• arrange pastry squares on a parchment-lined baking sheet. spoon the cooled mushroom filling into the center of each square and shred gruyere over the top. if the puff pastry seems a little warm and tacky, let the tarts chill in the fridge for ~5 minutes before baking (if they’re too warm they won’t puff right!)
• brush the borders with egg wash and bake at 400F for 18–22 minutes, until puffed and golden brown.
• let cool slightly, then garnish each mushroom puff pastry tart with a small dollop of crème fraîche and a sprig of thyme