My family absolutely love this dish..two of their favorites in a creamy sour cream Dijon sauce. Our favorite versions are done using fresh tuna, mahi mahi, or salmon, with the fish being grilled on a charcoal grill. With the cold, wet weather today, I pan fried the fish in a little butter and I used tilapia. It is fairly quick to throw together. I serve it with fresh spinach sauteed in butter, olive oil, garlic, and a little sea salt. I sometimes double the sauce ingredients as we are a saucy kind of family. Any remaining sauce is good over steamed broccoli or sauteed spinach.
Thaw fish if using frozen. Allow fish (either fresh or frozen) to come to room temperature. This makes for less time over the heat, helping to keep fish moist. Rinse and pat dry and lay on paper towels.
Place 2 tablespoons of the butter and 1/2 tsp each of onion salt, dried marjoram and dried thyme in a small bowl. Cover with a paper towel and microwave for 30 seconds to a minute, until butter is melted.
Brush top side of each fish fillet with half of the melted butter mixture and set aside.
In a medium saucepan, heat enough water to cover the shrimp and bring the water to a boil. Add the shrimp. Once the water comes back to a boil, cook the shrimp for 2-1/2 to 3 minutes, just until they are done (don't overcook). Remove pan from heat and set aside. (the water will help keep the shrimp warm...so it is very important not to over cook the shrimp).
In a small saucepan, combine the sour cream, flour, Dijon mustard, salt, pepper, and 1/4 tsp. thyme. Stir until smooth. Add chicken broth, stirring until well mixed. Cook over medium heat, stirring occasionally until thickened and bubbly. Cook and stir 1 minute more. Keep warm over very low heat, stirring occasionally. (When I first put this over the heat, I begin heating up my skillet for my fish, and the fish cooks while my sauce is coming up to a boil and thickening).
While Dijon sauce is coming up to a boil, heat a large skillet coated lightly with cooking spray over medium heat. Add remaining 2 TBS butter. Once butter is melted, add fish fillets, basted side down, with the thickest portion toward the center of your pan. Baste the top with the remainder of the basting sauce. Depending on your fish choice and its thickness, cook the fish for 2 to 4 minutes, just until a nice light brown color. Carefully turn the fish over (with the thickest portion still in the center of your pan) and cook another 2 to 4 minutes, just until the fish flakes easily with a fork. Remove to serving plates. (My tilapia fillets were 1/2 inch thick at the most and about 4 ounces each. I cooked 2 minutes on one side, 3 minutes on the other and they were perfect.)
Drain shrimp and stir into the Dijon sauce. Top each fillet with 6 shrimp each and some of the sauce. ENJOY!