WHITE BUTTER SAUCE
1/4 cup white or red wine vinegar
1/4 cup dry white wine or vermouth
3 TB shallots
3/4 lb chilled butter
salt and pepper
Reduce vinegar, wine, and shallots until liquid just films bottom of saucepan. Turn heat very low. Add chilled butter, piece by piece, slowly. Season with salt and pepper. For additional sauce, add more butter.
Place opened oysters on rock salt or crumpled aluminum foil in large baking pan.
Cook frozen chopped spinach in butter.
Put oysters in preheated 450-degree oven for 4 minutes, or until just plumped up.
Remove and cover with 1-2TBS spinach mixture. Coat with butter sauce and serve immediately.
Microwave spinach 8 minutes, turning once.
Heat 3 TB vinegar, 3 TB wine, shallots.
Swirl in 1/2 stick butter in pieces.
Bake oysters at 450 for 4 minutes.
Cover with spinach and sauce. Bake one minute more.