Saute the scallions and garlic in the oil for five minutes. Add the bacon and cook it until it and the garlic are lightly browned. Add the chicken stock and cook over high heat until it has been reduced to half a cup (about 15 minutes) and the garlic cloves are soft.
Meanwhile preheat the oven to 425 degrees. Slice the potatoes very thin (you will need enough to cover the surface of the fish fillets). If necessary, slice more later if you find you have not done enough. Toss the slices in the olive oil.
Peel the garlic cloves. Spread the garlic-bacon mixture over the bottom of a large heavy-bottom baking pan. Lay the fish fillets skin side down on top. Sprinkle with thyme, salt and pepper. Arrange the potatoes in barely overlapping layers on top of the fish fillets. Season with salt and pepper and bake, uncovered, for 10 to 15 minutes or until the potatoes are cooked. Sprinkle with parsley and serve.