In a medium saucepan, heat 1 tablespoon of the olive oil. Add the shallot and cook over moderate heat until softened, about 4 minutes. Add the thyme sprig, black pepper, red wine and balsamic vinegar and boil over high heat until reduced to 2 tablespoons, about 12 minutes. Remove the pan from the heat and whisk in the cream, then whisk in the butter, 1 tablespoon at a time. Season the sauce with salt and pepper. Strain into a bowl and keep warm.