Rinse and thoroughly dry the scallops. Drying is important because the scallops will not sear properly if they are full of water.
Heat a large cast iron skillet over medium high heat.
Add 2 tbsp of butter to the skillet.
Season the scallops with salt and pepper.
Place all the scallops on to the hot skillet and sear both sides for 2-3 minutes each.
Remove the scallops to a plate.
Reduce the heat to medium and melt 4 tbsp of butter in the skillet.
Add the mushrooms, shallots, and garlic to the butter and sauté until tender.
Sprinkle the flour over the softened mixture and stir to coat. Cook for 2-3 minutes.
Deglaze the pan with pinot grigio, scraping the bottom to remove any brown bits.
Add the oregano and heavy cream to the sauce and simmer for 5 minutes.
Return the scallops to the skillet.
Turn off the stove but leave the skillet on the burner it was cooking on.
Preheat the broiler to high.
Place 4 oven safe ramekins on to a sheet pan.
Fill each ramekin with 5-6 scallops and cover with mushroom sauce.
Shred about 2 tbsp of gruyere cheese over the top of each ramekin.
Broil for 3-4 minutes, or until the cheese is hot, bubbly, and crusting on top.
Remove from the oven and allow to cool for 5 minutes before serving.