01 -
Heat olive oil in a skillet over medium-high heat. Season beef cubes with salt and black pepper, then sear for 2 to 3 minutes on each side until browned. Remove from the skillet and allow to cool.
02 -
In the same skillet, sauté mushrooms, shallots, and garlic until mushrooms are golden brown, about 5 to 7 minutes. Stir in thyme, season with salt and black pepper, then transfer mixture to a plate to cool.
03 -
On a lightly floured surface, roll puff pastry sheets to approximately 1/8 inch thickness. Cut into 3 by 3 inch squares.
04 -
On each pastry square, place a small portion of mushroom duxelles, spread Dijon mustard if using, and top with a beef cube. Fold the pastry over and seal the edges securely with a fork.
05 -
Preheat oven to 400°F. Arrange assembled bites on a baking sheet lined with parchment. Brush tops with beaten egg and bake for 15 to 20 minutes until pastry is golden brown.
06 -
Remove from oven and allow to cool slightly. Serve warm for optimal flavor and texture.