Season scallops on both sides with salt, pepper and garlic, and lightly dust with flour. In a cup, combine miso, mirin, soy sauce, sugar and enough water (1 to 2 tablespoons) to give a pourable consistency; set aside. Arrange watercress on a serving plate as a bed for scallops.
Heat oil in a large skillet over medium-high heat. Sear scallops on both sides until lightly browned and just firm, about 4 minutes a side. Turn off heat, and remove scallops to a plate.
Pour wine into skillet, and stir, scraping up any browned bits from bottom of pan. Add miso mixture to pan, and bring to a boil over high heat, stirring. Turn off heat, and stir in mustard and cream.
Place scallops on watercress, drizzle warm sauce on top and shower each scallop with cheese. Serve warm.