Question: When is it possible that making one brocha would require you to make nineteen more brochas?
The gemorah in Brochas 33a says that we are required to make havdala twice after Shabbos. Once during davening (“Atta Chonantanu”) and once after davening with a cup of wine. If you forget the first time during davening, you do not need to daven again, because you are still able to make havdala afterwards with a cup of wine.
The gemorah in Pesachim 105a says that it is forbidden to eat or drink (with exception to water) before making havdala. If someone did eat, he can still make havdala. This is only if you said havdala during davening. If however someone forgot to say havdala during davening and then ate before saying havdala with wine, the halacha is that you must repeat Shmoneh Esrei before saying havdala with wine.
Therefore, to answer the above question, if someone forgot havdala during davening, and then made a “shehakol” to eat something, he is required to repeat the nineteen brochas of Shmoneh Esrei.

Rabbi Tzvi Aryeh Hyman, Mir Yeshiva
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