This is a really nice dish that combines acid, salt, and aromatics. It's really decadent and is great for special occasions like Valentine's Day, an anniversary, or a date night. I know you're going to love it.
Make the compound butter: Remove the inner stem of the chard leaves and roughly chop. In a skillet, heat two tablespoons of butter and saute the Swiss chard until wilted. Season with a pinch of salt. Set aside to cool. Finely chop the bacon and place in a bowl along with the butter. Add the lemon juice to the bacon/butter mixture. Finely chop the garlic and mix into the bacon/butter along with the Parmesan, thyme, and chives. Season with salt and pepper. Finely chop the chard and fold into the butter mixture. Taste and adjust the seasoning with salt and pepper. Set aside. (To store, form into a log, wrap in plastic and place in the refrigerator. Soften first before using on oysters).
Shuck the oysters: Using an oyster knife, locate the “keyhole” in the top of the oyster. Stick the tip of the knife into the keyhole and wiggle it until until the top releases. Wedge your finger along the side of the oyster (it won’t hurt!), just to open it enough to run the knife along the edge. (This will keep the oyster from puncturing as it’s opened.) Shuck the oysters, leaving the connector muscle attached, so they stay in place for baking.
Bake the oysters: Preheat oven to 450 degrees F. Fill a deep cast iron skillet halfway with sea salt or rock salt and place in the oven to come up to temperature. Pull the heated rock salt dish from the oven. Carefully place the oysters on the salt and dollop with a generous amount of the compound butter. Place in the oven for about 6-8 minutes, until the butter melts and the oysters are slightly curled. Finish with freshly grated Parmesan cheese and serve right out of the hot casserole.