Challah is separated after the flour and liquid are well mixed together, while the dough is still whole, before it has been divided and shaped into loaves. If the dough has been kneaded in several batches, combine it all in a single bowl.
If the conditions for reciting the blessing are met, recite the following (if you do not understand the Hebrew, you can recite the blessing in English, or in any other language you understand):
Hebrew and English:
Blessed are You, L-rd our G‑d, King of the Universe, who has sanctified us with His commandments and commanded us to separate challah.
בָּרוּךְ אַתָּה יְיָ אֱלֹהֵינוּ מֶלֶךְ הָעוֹלָם, אֲשֶׁר קִדְּשָׁנוּ בְּמִצְוֺתָיו וְצִיוָּנוּ לְהַפְרִישׁ חַלָּה.
Transliteration:
Bah-rookh ah-tah ah-doh-nai eh-loh-hay-noo meh-lekh hah-oh-lahm ah-shehr keed-shah-noo bi-meetz-votahv vi-tzee-vah-noo li-hahf-reesh khah-lah.
Separate a small piece of dough, approximately one ounce, and say: "This is challah."
Burn the challah by wrapping it in a piece of silver foil and placing it in the broiler, or by any other method. (If burning it inside the oven, there should be no other food baking in the oven at the same time.)
If the purpose of burning the challah is to ensure it is not used, can one simply throw it away? Why is burning necessary?
Also is there any discussion given how many people are hungry of using this dough (I realize it’s a small amount but) to feed someone instead of wasting it?
The mitzvah derives from the Torah’s laws of terumah, where terumah (and challah, which is a form of terumah) that is tamei (ritually impure) must be burned, not discarded. Simply throwing the challah away is not considered correct except in extenuating circumstances. Burning is the preferred method, as it is an act of kavod (honor) for the mitzvah and ensures no inadvertent benefit is derived from the sacred dough.