While on holiday in Indonesia I had this for the first time (I believe it was in Bandung).... whoa, soooo good. I found a recipe. Source: all recipes for you.

Combro is the typical food of West Java, Indonesia. Made from grated cassava that the inside is filled with sambal oncom then fried, because that is named combro which is short for oncom in jero (Sundanese, means: oncom insied). Round oval shap. This food is delicious when eaten warm.

1 kg grated cassava
1/2 grated coconuts
1 teaspoon salt

4 pieces of onion and
2 gloves garlic mashed
a small bowl tempe cake/oncom, cut into small pieces
cayenne pepper according to taste
3 stalks green onion chopped
3 stalks celery chopped

soy sauce
sugar to taste (substitute msg)

How to cook:
Grated cassava is mixed with grated coconut, salt and sugar. Saute onion and garlic finely, and enter oncom, salt, pepper, sweet soy sauce, flavoring cooking chili pepper, green onion and celery. Take a ping-pong ball of dough and fill with batter pipihkan content, oval and round shape and fry in hot oil.