DIRECTIONS
Preheat oven to 375 degrees.
Lightly butter a medium sized dish, about 8 by 12 inches.
In saucepan over medium-low heat, melt the butter.
Stir in the flour to make a roux and cook, stirring constantly for 2 to 3 minutes.
Gradually whisk in the milk.
Raise the heat to medium and bring the mixture to a simmer, whisking frequently.
Cook until thickened into a white sauce, about 10 minutes.
Whisk in 1 tsp. salt and pepper to taste.
Cover and set aside.
In a small stockpot, place the spinach, cover and cook until wilted, about 3 minutes.
Empty into colander and run cold water to cool.
In small handfuls, squeeze as much water from the spinach as possible.
Chop the spinach finely.
Transfer to a bowl and stir in 1/2 cup of the white sauce.
Season with salt and pepper to taste.
Lay out 4 fillets, smooth side down, checking and discarding any bones you may find.
Spoon 1/4 of the spinach mixture onto the center of each fillet; fold the 2 ends of the fillet over the top of the spinach.
Transfer each fillet into prepared dish, seam side down.
In a blender combine all but a 1/4 cup of shrimp, the remaining white sauce, the stock and the tomato paste.
Puree until smooth.
Place in bowl and season with salt and pepper.
Pour the sauce over the fillets; bake 25 minutes.
Sprinkle the remaining shrimp on top of the fish; bake 5 minutes longer.
Sprinkle with chives.
Serves 4.