Season Perch fillets with salt and pepper. 

Sauté onion in butter. 

Add spinach leaves and saute until liquid is gone. 

Add basil, garlic, olives, and lemon juice. 

Sauté until heated through.  Set aside to cool.

To assemble:

Use 2 filo sheets per serving.  Open the sheets and place the fish on one end. 

Top with a portion of the spinach mixture and crumble 2 Tbsp. of feta cheese on top. 

Fold the filo around the fish to form a packet. 

Place on a sheet pan and drizzle with butter.

Bake at 450 for approximately 10-12 minutes.