Raw Kale - Korean side dish
Not sure if this is what you are looking for, but thought I'd post that in researching, I found that Korean side dishes are called banchan, and the specific dish that you are speaking of might be kale namul:

Kale namul 케일나물 (Korean Seasoned Kale)

Makes 2 cups

1 pound kale
1 green onion
1 clove garlic, finely minced
1 tsp. soy sauce
1 tsp. roasted sesame oil
½ tsp. roasted sesame seeds
salt, to taste


http://www.apricosa.com/2011/03/different-sort-of-namul.html

The sweetness you refer to might just come from the kale itself, depending on the varietal.