In a decent restaurant, do you mean a proper restaurant ?? or a Mehana (tavern) ?? proper restaurants, the Victoria, Chateau Antique, Premier, in fact a number of hotels have decent restaurants... Mehanas, Dedo Penne, Bariakova, Banski Han etc etc etc.... there are many
I would recommend Amvrosia. It is a nice change to the mehanas, although the prices are higher than usual but on the other hand you get extremely good food and nice service. Also they have free transfer to the restaurant so you do not walk. Really loved it.