Often the common name in a recipe, or a translation is worse than useless; the translation leads you to a non-edible plant.
From a Korean cooking site:
The root of this species (radix platycodi) is used extensively in as an anti-inflammatory in the treatment of coughs and colds. In Korea the plant is known as DoRaJi (도라지) and its root, either dried or fresh, is a popular ingredient in salads and traditional cuisine.
See, what most gardeners call 'Bellflower' is often a Campanula.
But the plant used in these recipes is not a Campanula, but is Platycodon grandiflorus, more commonly known around here as Balloon Flower. (Wikipedia)
Easy to grow, by the way, for flowers. I have no idea if the roots would grow into a nice harvest.