Heat 1 tablespoon of olive oil in a skillet over medium-high heat. Season the beef with salt and pepper, then sear it for 2-3 minutes on each side until browned but still rare in the center. Remove the beef from the skillet and let it cool on a cutting board for about 10 minutes.

In the same skillet, add another tablespoon of olive oil, then toss in finely chopped mushrooms, shallots, and minced garlic. Sauté the mixture for 5-7 minutes until the mushrooms are golden and their moisture is released. Sprinkle in fresh thyme, salt, and pepper to taste, allowing the duxelles to cool completely before using.

On a lightly floured surface, roll out the puff pastry until it’s about 1/8 inch thick. Use a sharp knife or pastry cutter to cut the dough into 3x3 inch squares.

Place a spoonful of the mushroom duxelles in the center of each pastry square, followed by a piece of the cooled seared beef. Optionally, brush a little Dijon mustard on the beef for added flavor. Fold the pastry over to encase the filling and use a fork to crimp the edges tightly.

Preheat your oven to 400°F (200°C). Arrange the assembled Mini Beef Wellington Bites on a baking sheet lined with parchment paper. Brush the tops with beaten egg. Bake for 15-20 minutes, or until the pastries are puffed up and golden brown.

Once baked, carefully remove the mini beef Wellington bites from the oven and let them cool for a few minutes on the baking sheet before serving warm with your favorite dipping sauces.