Baked Stuffed Sole with Shrimp Sauce

INGREDIENTS

• 6 Tbs. (3/4 stick) unsalted butter, plus more for
• greasing
• 1/4 cup all-purpose flour
• 2 cups milk
• 1 tsp. sea salt, plus more, to taste
• Freshly ground white pepper, to taste
• 1 lb. spinach, stemmed and well washed but not
• dried
• 4 sole fillets, each about 6 oz.
• 1/2 lb. cooked cocktail shrimp
• 1/2 cup chicken stock or low-sodium chicken
• broth
• 1 Tbs. tomato paste
• Pinch of cayenne pepper, or to taste
• Minced fresh chives for garnish