The Rabbi's reason to make the bread cook fast, from start to finish in 18 minutes? 18 minutes is the amount of time it takes to keep all yeast out. What they don't seem to realize is that they have created the perfect symbolism that God initiated long ago.
The Feast of Unleavened Bread is a feast that is generally mistaken for Passover. Passover however is only one 24 hour period while Feast of Unleavened Bread lasts for seven days.
On the evening after Passover God told the Hebrew people exiting Egypt not to allow their bread to rise, but to grab everything and leave. The ancient peoples used to gather yeast on grape leaves to leaven their bread if they needed to speed up the process, but God said "Don't even let any leavening touch the dough. Just bake it and go."
In their haste they grabbed the necessities and fled toward the land God was preparing for them.
God then told them that in the future they were to commemorate this feast by getting all yeast out of the house for seven days.
On a normal Passover eve a family that celebrates the Biblical feasts will leave a bit of bread in their home in hidden places for the children to find. The children will search out the yeasty creations till they "eradicate" the yeast from the house. The family then takes what is found and burns it outside. MORE