Drain oysters, reserving 3 tablespoons oyster liquor. Chop 4 oysters; set remaining oysters and oyster liquor aside.
Melt 1 1/2 tablespoons butter in a heavy saucepan over low heat; add flour, stirring until smooth. Cook 1 minute, stirring constantly. Dissolve soda in whipping cream; gradually stir into flour mixture with reserved oyster liquor. Cook over medium heat, stirring constantly, until thickened and bubbly. Stir in chopped oysters, 1/4 teaspoon salt, and 1/8 teaspoon pepper. Set aside, and keep warm.
Melt remaining butter in an 8- inch omelet pan or heavy skillet over medium heat; add reserved oysters, and sauté 1 minute. Drain oysters; set aside and keep warm.
Combine eggs, milk, remaining salt, and pepper in a small mixing bowl; beat well. Pour egg mixture into omelet pan or skillet. Cook over medium heat, lifting edges of omelet and tilting pan to allow uncooked portion of omelet to flow underneath.
Cook until egg mixture is set and no longer flows freely; place reserved sautéed oysters over half of omelet. Fold omelet in half over oysters; transfer to a warm serving platter. Serve immediately with reserved oyster sauce.
Note: Repeat procedure for additional servings.