For the caper, shiitake and green onion relish: Combine the shiitakes, green onions, olives, shallots, soy sauce, capers, garlic, chile flakes, mirin and sesame oil in a bowl and refrigerate overnight.
When you are ready to cook, remove the relish from the refrigerator and bring it to room temperature, 20 to 30 minutes. Adjust the seasoning with salt and pepper.
For the seared scallops: Score the scallops on one side with 4 small cuts in a hashtag pattern (#). Place the scallops on a towel and dry both sides.
Heat the grapeseed oil in a skillet over high heat. Season the scallops with salt and pepper, add to the skillet and sear for 1 minute per side.
Remove the skillet from the heat, add the butter and baste the scallops to finish cooking, 1 to 2 minutes.
Place the relish on a plate and arrange the scallops around it.
For the salad: Combine the alfalfa sprouts, green onions, lemon juice and olive oil in a bowl. Add salt and pepper and toss to combine.
Place the salad in the center of the scallops. Serve immediately