Boil beets in a large, heavy saucepan until tender. Remove cooked beets to a bowl of cold water. When cool enough to handle, slip off skins and discard. Slice or chop beets. In a small skillet or saucepan over medium heat, cook ginger and sesame seeds in oil, stirring constantly, for 1 minute. Remove pan from heat and stir in miso and 1/4 cup beet cooking liquid. Cool dressing mixture slightly before adding lemon juice. Toss dressing with beets until well coated.