1. Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper. This sets the stage for perfectly golden pastry.
2. Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Season the beef cubes with salt and pepper, then sear them for about 1-2 minutes on each side until browned but not cooked through. Remove and let cool. This quick sear locks in the juices—something my grandmother always emphasized.
3. In the same skillet, add butter, shallots, garlic, and mushrooms. Cook over medium heat until the mixture is dry and concentrated, about 8-10 minutes. Stir in thyme, then season with salt and pepper. This mushroom duxelles is the heart of flavor, and taking the time here really pays off.
4. Roll out the puff pastry on a lightly floured surface to smooth any creases. Cut the pastry into squares large enough to wrap each beef cube (roughly 3×3 inches).
5. Brush each beef cube with Dijon mustard, then place it in the center of a pastry square. Top with a spoonful of mushroom duxelles.
6. Fold the pastry over the beef, sealing the edges by pinching or pressing with a fork. Make sure each bite is tightly wrapped to avoid any escaping juices.
7. Place the wrapped bites seam-side down on the prepared baking sheet. Brush each with beaten egg to ensure a golden, glossy finish.
8. Bake for 15-18 minutes, or until the pastry is puffed and golden brown. Keep an eye on them—every oven is different, and you want that perfect balance of flaky crust and tender beef.
9. Remove from the oven and let cool for 5 minutes before serving. This rest time helps the juices redistribute, making each bite even more delicious.

One thing I’ve learned over the years is to not rush the resting step—especially with beef. My husband always teases me for letting food sit, but it’s the secret to juicy, tender bites every time.