Step 1

Heat the oven to 400°F.

Step 2

Melt the butter over medium heat, then sauté the mushrooms and onions, stirring occasionally, until all the liquid evaporates, about 8 minutes.

Step 3

Generously sprinkle with salt and pepper. Add the flour and cook for 30 seconds to 1 minute, stirring constantly, to get rid of the raw flour taste.

Step 4

Add the cream and simmer, stirring often, until thickened, 1 to 3 minutes. Season with salt and pepper to taste. Let cool to room temperature (spreading on a plate and popping in the fridge or freezer speeds this up).

Step 5

Roll each puff pastry sheet into a 10-inch square. Cut each into 2x2-inch squares (yielding about 50 total—it’s okay if they’re not perfect). Fill each with 1 teaspoon of the mushroom mixture, then bring the corners together and squeeze shut to create a bundle. Place into a mini muffin pan.

Step 6

Bake for 25 to 30 minutes, until golden brown. (Bake for an additional 5 minutes or so if baking from frozen.)

Step 7

Serve hot, warm, or at room temperature.