Isn't it gorgeous? I made it all by myself today!
Kudos to Shaindy and her family, also known as my other family, for letting me in on their minhag to bake Challah with a Key in it (schlissel is yiddish for key) on the Shabbos after Pesach.
Over at A Simple Jew, I found the following reasons for this supercool minhag (which like Shaindy's family, I've decided to adopt as my own):
1).In Shir Hashirim (which we read on Pesach) it says פִּתְחִי-לִי אֲחֹתִי רַעְיָתִי - “Open for Me, My sister, My beloved". Chazal say that Hashem asks us to open up for Him a small whole like the tip of a needle and He will open up a huge hole for us. Also, Klal Yisroel is called a bride and they are called the bechina (aspect) of bread. During Pesach all the upper gates and minds are open and after Pesach they close and we need to open them. Therefore, we put a key in the challah after Pesach to hint at us opening a small “hole”, through the mitzvah of Shabbos (and, if I might add, the mitzvah of challah) and now Hashem should open up all His good from his storehouses and the heavens like He gave the mon to our fathers in the month of Iyar, and this Shabbos we bless the month of Iyar.
2) After Pesach is when the mon stopped falling and we brought the Omer. From then on we needed to eat from the produce of the ground; we needed parnasa, since untill now we had the mon. It is known that everything has a gate. Therefore just as we daven to Hashem to open up the gates of parnasa we have a minhag to put the form of a key on the challos to allude that Hashem should open up the gates of parnasa for us.
3) During sefira we count 49 days till Shavuos, the 50th day, which is the shaarei bina. We go from gate to gate, and each gate has a key. That is why we make an image of a key on the challah.
4) It says in Shir Hashirim 1:11 תּוֹרֵי זָהָב נַעֲשֶׂה לָּךְ עִם נְקֻדּוֹת הַכָּסֶף - "We will make for you circlets of gold with spots of silver." By the Mishkan it says זהב וכסף ונחשת, putting zahav (gold) before kesef (silver). In Bereishis, by the creation of the world, the first day it says Yehi ohr which is chesed (which is represented by silver) and the second day represents gevurah, which in turn represents gold. The reason is that by the creation of the world it was pure chesed, as it says “the world was built on chesed” (Tehilim 89,3), therefore chesed, which is representative of kesef, precedes gevurah, which is representative of zahav. By the Mishkan, however, Hashem had to, so-to-speak, contract (tzimtzum) the Shechina (Divine Presence) to dwell in it, and tzimtzum is from the aspect of gevurah, therefore zahav precedes kesef by the Mishkan. However, the zahav written there has the nekudah (vowel sound) of a פַתַּח (it has a patach instead of the usual kometz), it says זְהַב הַתְּנוּפָה (Shemos 38,24), and that is the nekuda of chesed –the nekuda of chochma. And פתח (the vowel) also means opening like פתח ושער- from there comes all the kindness. Putting it all together, this that we say in Shir Hashirim תּוֹרֵי זָהָב נַעֲשֶׂה לָּךְ עִם נְקֻדּוֹת הַכָּסֶף means the Mishkan was made with zahav, the aspect of tzimtzum, but with the nekuda of kesef, meaning the (word “zahav”, instead of having the usual vowel, kometz, is written with the) nekuda of patach, which is chesed. And the Shabbos after Pesach is always in the second week of sefira which is gevurah, the aspect of zahav, except that it is menukad with kesef, nekudas patach. Through this we say that we will open up all the gates of blessing and since every gate has a מפתח (key) we make the image of a key on the challah.
5) The previous four reasons are all brought by the Ohev Yisroel in Shabbos Acher Pesach and Likutim Parshas Shmini. There is a fifth reason brought by the Ohev Yisroel, also based on the posuk תּוֹרֵי זָהָב נַעֲשֶׂה לָּךְ עִם נְקֻדּוֹת הַכָּסֶף, connecting the written and oral Torah to challah. (See Ohev Yisroel, Shabbos Acher Pesach)
6) The matza we ate on Pesach is supposed to instill in us Yiras Hashem. And Yirah is compared to a key as we see from the following Gemara in Mesechta Shabbos 31a-b: “Rabbah bar Rav Huna said: Any person that has Torah but doesn’t have Yiras Shomayim is comparable to a treasurer who has the keys to the inner parts (of the treasure house) but the keys to the outer area was not handed to him. How can he get to the inner parts (if he can’t first get into the outer parts)?” Therefore we put a key in the challah the Shabbos after Pesach to show we want the Yirah obtained from the matzos to stay with us, because if one has Yirah then the Torah will stay attached to him. (Yismach Yisroel)
7) The Rambam lists out at the beginning of Hilchos Chometz U’Matza that there are 8 mitzvos (3 positive & 5 negative) involved there. The key we put in the challah alludes to this Rambam: the letters of מפתח (key) spell פ״ת ח׳ מ׳צות. (פ״ת is bread, representing the “chometz” and מ׳ is for matza- these allude to Hilchos Chometz U’Matza, and theח׳ is the 8 mitzvos involved) (Tzvi LaTzadik)
8) The Shabbos after Pesach we make challos that look like matzos, as an allusion to the matzos that were eaten on Pesach Sheini. And we put a key in it to allude to the “gates” being open untill Pesach Sheini. (Imrei Pinchos)
9) The minhag is to put keys in the challah and make them in the form of matzos. The reason is that in these seven weeks of sefira we are supposed to work on our Avodas Hashem until we reach the the level of the first night of Pesach. The way to do this is to put the “left into the right”, meaning mix the trait of ahava (right side) with yirah (left side). In this second week of sefira we have these two traits in our hands, since the first week of sefira is chesed- ahava, and the second week is gevura - yirah. That is why we make the challah look like matza. Matza is representative of the yetzer tov, the right, and chometz is representative of the yetzer horah, the left. Now, we have challos which are true chometz, in the form of matza; “the left is in the right”, chometz in matza. (Shearis L’Pinchos)
10) There are many reasons given for the shlissel challah, and I say that the shlisel challos are the keys to parnasa. (Segulas HaBeShT V’Talmidov quoting Nachlas Yaakov)