Shrimp Stroganoff

1/4 cup minced onion
5 tablespoons butter, divided
1 1/2 pounds shelled, raw shrimp
1/2 pound fresh mushrooms, quartered
1 tablespoon flour
1 1/2 cups sour cream (at room temperature)
1 1/4 teaspoons salt
Pepper, to taste
Cooked yellow rice
Artichoke hearts, quartered

In a large skillet sauté onion in 1/4 cup of the melted butter until softened. Add shrimp and sauté for 3 to 5 minutes or until pink and just cooked. Transfer mixture to a heated dish and keep warm.

In the same skillet sauté mushrooms in remaining butter over moderately high heat until browned. Sprinkle mushrooms with flour and cook mixture, stirring, for 2 minutes. Reduce heat to moderately low and stir in the shrimp mixture, sour cream, salt and pepper. Cook mixture, stirring, for 2 to 3 minutes or until shrimp are thoroughly heated. Do not let mixture boil. Serve immediately over saffron rice tossed with quartered artichoke hearts.