Bubba Gump Shrimp Co Shrimp Etouffee

Found the recipe here.

2 pounds unpeeled medium fresh Shrimp
3 cups Water
2 cup chopped Onion
4 cloves Garlic peeled and minced
2 tablespoons Butter melted
1 cup slices Green Onions
3 tablespoons Cornstarch
1/3 cup chopped fresh Parsley
3/4 teaspoon Salt
1/4 teaspoon freshly ground Black Pepper to taste
Hot Cooked Rice, enough for 8 servings to serve
Parley to garnish
Lemon Wheels or Wedges to garnish

Peel and devein shrimp, reserving the shells and tails. Set shrimp aside.
Place shells and tails in a medium saucepan.
Add water.
Place saucepan over medium heat and bring to a boil. Cover, reduce heat, and simmer for 30 minutes.
Pour the liquid through a wire mesh strainer into a bowl, discarding the shells and tails. Set strained stock aside.
Place prepared onion and garlic in a large skillet.
Add melted butter.
Place skillet over medium high heat. Stirring constantly, sauté onions and garlic until tender and fragrant.
Add 2 cups of the reserve stock. Bring to a boil. Reduce the heat to low. Stir in prepared shrimp and green onions. Cook 5 minutes, stirring occasionally.
In a small bowl or cup, combine cornstarch and an additional 1/2 cup of the reserved stock. Stir to mix well.
Gradually stir cornstarch mixture into shrimp mixture. Bring back to a boil, stirring constantly, 1 minute.
Stir in the parsley, salt, and pepper, to taste.
Serve over rice, garnished with parley and a lemon wheel or wedge.