The combination of mochiko and the other ingredients should lend to a chewy waffle. There can be a few troubleshooting ideas that may be why your waffle did not turn out chewy. One of which is that you have too much regular flour and not enough sweet rice flour. Another reason that may cause the waffle to be hard or dense is that the rice flour has gone bad. Also, baking powder and cornstarch are needed to ensure a texture that is known when making mochi baked goods.