Spread a thin layer of jam on each slice of bread and fold in half to form sandwiches. In a bowl, combine milk, vanilla, liquor, salt and eggs. Dip sandwiches into batter and soak briefly. Over medium heat, heat a non-stick skillet and melt a tablespoon of the butter. Cook the sandwiches in batch, cooking on both sides until golden, adding more butter to the pan for each batch. Place sandwiches on a platter and keep them warm in the oven until all are cooked. Dust with powdered sugar. Serve with syrup and sour cream.