In a frying pan, cook the streaky bacon until crisp. Once cooked to your liking, remove to a piece of kitchen towel.
In the same pan, cook the scallops in the bacon fat. Get the fat hot (but not too hot, it will spit) and place the scallops into the pan. Don't overcrowd the pan, or the scallops will steam rather than sear. Cook for two minutes, and then flip. Once flipped, add a small knob of butter to the pan. Cook for a further one to two minutes until the scallops are cooked through but still tender.
Take two slices of bread, brown or any other that you fancy, and build the sandwich with a layer of bacon, the warm scallops and some of the salty juices. Serve immediately.