Making Beef Wellington Turnovers can be streamlined if you follow these simple steps:

1. Cook the Beef: In a skillet, heat olive oil over medium-high heat. Sear the beef cubes for 3-5 minutes until browned. Remove from heat and set aside to cool.
2. Prepare the Mushroom Mixture: In the same skillet, add the onions and garlic. Sauté for 2-3 minutes until softened. Then, add the finely chopped mushrooms and cook until the moisture evaporates, about 5-7 minutes.
3. Flavor the Mixture: Stir in the Dijon mustard, thyme, parsley, salt, and pepper into the mushroom mix. Add the seared beef and combine well. Allow the mixture to cool down completely.
4. Prepare the Puff Pastry: Roll out the thawed puff pastry sheet on a lightly floured surface. Cut it into squares, approximately 4 inches x 4 inches.
5. Fill the Pastries: Spoon the beef and mushroom mixture onto the center of each pastry square, leaving a border around the edges.
6. Seal the Edges: Fold the pastry over to form a triangle or rectangle, depending on your preferred shape. Press the edges to seal tightly, and use a fork to crimp the edges for extra security.
7. Apply Egg Wash: Brush the tops of the turnovers with the beaten egg to give them a beautiful golden finish once baked.
8. Preheat the Oven: Preheat your oven to 400°F (200°C).
9. Bake the Turnovers: Arrange the turnovers on a parchment-lined baking sheet and bake for 25-30 minutes or until golden brown and puffed up.
10. Cool and Serve: Allow the turnovers to cool for 10-15 minutes before serving. Enjoy!

These steps should help you create these incredible Beef Wellington Turnovers with ease.