First of all, put the cornstarch and flour into a bowl, add yeast and baking powder and mix well; add warm water and form a dough, and put it in a warm place with a plastic sheet to rise; when the dough has risen for an hour or so, you can take it out and knead it a bit and cut it into strips; roll the dough into a round shape, and use a knife to cut it into two different sizes of small dosages; press the bigger dosage into a cake shape; roll the smaller dosage into a round shape, and use an oil brush to wipe 3/4 of the small dosage with oil and put it on the cake; use one hand to drag the crust, and the other hand to press the smaller dosage into the cake shape; use an oil brush to brush the smaller dosage with oil. Put 3/4 of the small dosage on oil, put it on the big dosage pressed into cake shape; drag the dough with one hand, press the small dosage with the other hand, turn the dough while pressing, so that the dough will be wrapped around the small dosage of the 3/4 of the dab of oil on the dosage, and a mixed grain bread embryo is completed; the next thing you need to do is to put the good mixed grain bread embryo on the steaming plate to wake up for fifteen minutes, and then take out of the steaming pot over high heat for fifteen minutes and gently press with your hand! can be a small dose of dough out, the rest is the finished mixed grain bread!