Creating Spinach & Cheese Stuffed Salmon Wellington is simple if you follow these easy steps:

1. Preheat Oven: Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
2. Prepare Filling: In a mixing bowl, combine the chopped spinach, cream cheese, mozzarella cheese, minced garlic, lemon juice, dried dill, salt, and pepper. Mix until well blended.
3. Prepare Salmon: Pat the salmon fillets dry with a paper towel. Season both sides with salt and pepper.
4. Roll Out Pastry: On a lightly floured surface, roll out the puff pastry sheet until it is large enough to wrap around the salmon.
5. Assemble: Place one salmon fillet in the center of the pastry. Spoon half of the spinach and cheese mixture on top of the salmon. Top with the second salmon fillet and then add the remaining filling.
6. Wrap Salmon: Carefully fold the pastry over the salmon, sealing the edges well to prevent any filling from leaking out. Use a fork to crimp the edges for a decorative touch.
7. Apply Egg Wash: Brush the top of the pastry with the beaten egg for a beautiful golden finish.
8. Bake: Place the wrapped salmon on the prepared baking sheet and bake for 30-35 minutes, or until the pastry is golden brown and flaky.
9. Cool: Remove from the oven and allow to cool for 10-15 minutes before slicing.
10. Slice and Serve: Cut the Wellington into thick slices and arrange on a serving platter.

These straightforward steps will guide you in creating an incredible Spinach & Cheese Stuffed Salmon Wellington that will leave your guests impressed!