Preheat the oven to 400°. If you have scallop shells for baking, spritz them with some vegetable spray, place on a baking sheet and set aside. If you're not using scallop shells, use a ceramic baking dish that will fit the scallops in a single layer without crowding and lightly spray with vegetable spray. Set aside.
Tear the sourdough bread into chunks and add it to the bowl of a mini prep food processor. Pulse several times until you have breadcrumbs. Set aside.
Heat a small saute pan over medium heat. Add the diced pancetta and cook until crisped and fat has rendered. Transfer the pancetta to a dish lined with paper towels. Reserve 1 teaspoon of the rendered fat and discard the rest. Add the shallots and 1 tablespoon of butter to the pan. Saute until the shallots are softened and translucent. Add the white wine and vermouth and cook until the liquid has reduced by half, about 3-4 minutes.
Add 3/4 cup breadcrumbs, pancetta and parsley to the shallot mixture and toss to coat.
Place 1-2 scallops in each of the scallop shells or lay them in the baking dish. Sprinkle the breadcrumb mixture over the top of the scallops.
Add one teaspoon of butter to the remaining breadcrumbs in the food processor and pulse 3-4 times until butter is incorporated with the breadcrumbs. Sprinkle the buttered breadcrumbs over the scallops.
Bake for 15 minutes or until the scallops are cooked to desired doneness. Sprinkle with parsley and serve.