Preheat the oven to 400 degrees.
First, 1/2 lemon juice, salt and pepper all 4 pieces of salmon and set aside.
Now, mix the spinach, sour cream, lemon juice, garlic powder, salt and pepper in a bowl.
Next, cut both pieces of puff pastry in half. This should give you 4 rectangles. Brush Dijon mustard on the side facing up (repeat for all 4 pieces).
Now, place salmon in the middle of the puff pastry (side with Dijon mustard). Then top with 1/4th of the spinach mixture. Next, pull the dough around the salmon and sealing all edges with your fingers (like wrapping a present).
Repeat above process for other 3 pieces of salmon, puff pastry and spinach mixture (see video above).
Next, Place the all 4 of the puff pastry wrapped salmon seam side down on a sheet tray.
Now, brush egg on top of each puff pastry package and then sprinkle with sesame seeds on top.
Finally, Bake in middle rack for 20 minutes.
Happy Eating.