Most of Yogyakarta's dishes are sweet but you could try Oseng-Oseng Mercon Bu Narti which is very spicy and tasty! You may also try Jejamuran; all of their dishes are made from mushrooms; including Pepes (mushroom is served in banana leaf package and cooked on steam), Tongseng (Surakarta dish which is usually made from beef/mutton stew in curry-like soup with vegetables and kecap manis), Satay (also made from mushroom). You may also try Waroeng SS (Spesial Sambal) which has several outlets in Yogyakarta. They have many varies of Sambals, perhaps around 20s different kind of Sambals. So, if you would like to try all of the sambals, perhaps you should visit it more than once.