Heat olive oil in a frying pan over medium heat. Add garlic and spinach carefully. Cook until spinach softens completely. Remove extra moisture and let the mixture cool slightly.

Place cooked spinach inside a bowl. Add cream cheese, dill, lemon juice, salt and pepper. Stir everything together until the filling becomes creamy, smooth and flavorful.

Pat the salmon fillet dry using paper towels carefully. Spread Dijon mustard lightly over the salmon surface. Season both sides with salt and black pepper evenly.

Lightly flour your work surface before rolling the puff pastry gently. Roll it slightly larger than the salmon fillet so it wraps fully around the fish.

Spread the creamy spinach mixture in the center of the pastry sheet evenly. Place the seasoned salmon carefully on top of the spinach filling mixture.

Fold the puff pastry around the salmon tightly but gently. Seal all edges carefully to prevent leaks. Place the wrapped salmon seam-side down onto baking parchment.

Use a pastry brush to coat the top with beaten egg evenly. This step helps create the beautiful golden and shiny pastry crust while baking.

Preheat oven to 400 degrees Fahrenheit. Bake the salmon wellington for about thirty minutes until the pastry becomes golden brown and crisp on every side.

Remove the wellington carefully from the oven. Let it rest for five minutes before slicing. Resting helps keep the filling and salmon moist inside.

Slice the salmon wellington using a sharp knife carefully. Serve warm with vegetables, potatoes or salad for a comforting and elegant homemade seafood dinner.