Early leaders of Reform Judaism thought that men and women had moved past ritual and ceremony. In the Liberal Jewish Synagogue in London and classical Reform temples in the United States the service was reduced to hymn singing, responsive prayers and a sermon. It soon became clear that this was leaving congregations cold.

In the past half-century, Progressive Judaism has returned to practical mitzvot. It does not generally regard them as binding, but important and meaningful nevertheless. There has been a realisation that we need tangible symbols and representations of the values we cherish and want to transmit.

Traditional Judaism has much the same attitude towards minhag — the established customs of the Jewish people. It is true that in some cases they carry the force of law; minhag Yisrael Torah hi is an ancient principle and the Talmud tells us that we should safeguard the customs of our ancestors. When Jews in the diaspora asked whether they needed to keep two days of Yomtov even after the fixing of the calendar, they were told to maintain their ancestral practice; minhag avotechem beyadechem, “your fathers’ customs are in your hands”.

In other cases, minhagim have no binding authority. Eating apples and honey on Rosh Hashanah or wearing a kittel on Yom Kippur are common and beautiful but not essential. We are about to enter a blaze of this type of more optional minhag.

Shavuot is crowded with customs: decorating the synagogue with flowers, staying up all night learning Torah (Tikkun Leil Shavuot) and eating milky foods. They are beloved traditions, and they have all been connected to the giving of the Torah. Mount Sinai burst into flower when the Torah was given. The night before the revelation the Jews overslept and we make a correction (tikkun) for that by learning until dawn. The first Shavuot fell on Shabbat. The Jews were unable to slaughter animals, and the meat they had in stock had not been produced according to the rules of kashrut, which had not yet been given. They therefore had to eat foods made from milk.

These are just three of many reasons; for example, the Zohar observes that the Hebrew word for milk, chalav, has the numerical value of 40 — the number of days Moses spent on Mount Sinai. The Imrei Noam (Rabbi Meir Horowitz of Dzikov) explained that Torah for the Jewish people is like mother’s milk to a baby, nourishing and the sign of love and care.

If a practice has many explanations, they are usually all inaccurate, at least in a strictly historical sense. The reason we have milky foods on Shavuot is probably because the festival falls in the calving season when there is a large amount of surplus milk.

We took advantage of this abundance by enjoying the festival with cheesecake, blintzes and the like. This is profoundly in keeping with the spirit of Shavuot. It is the only festival on which all the rabbis agree we have to enjoy ourselves physically as well as spending time in spiritual pursuits.

But why did we have to attach a more direct connection between Shavuot and cheesecake? One reason is that, without minhag, Shavuot would feel like rather a bare festival. The other Yomtovim have a distinctive mitzvah, whether it is matzah on Pesach, lulav on Succot or shofar on Rosh Hashanah.

Shavuot had bikkurim, the bringing of the first fruits, but that has not taken place since the destruction of the Temple. Jews did not want to go through a festival without performing some symbolic practice and so they produced new minhag and attached meaning to existing practices, like eating milk. This may be why there is so much minhag associated with Shavuot; it is compensating for the lack of mitzvot.

However, there is more to it than that. The Jews are a religious people. We seek spiritual meaning wherever it can be found and we display a wonderful creativity to generate it. It is anything put trivial to turn eating cheesecake into a religious experience, it is an example of the Jewish genius. The origins of the practice of eating milky foods has become irrelevant. We have imbued it with meaning, we have sanctified it, we have enabled ourselves to connect with the message of Shavuot, even while we are eating dessert.

Rabbi Shlomo Ephraim Luntschitz, a leading rabbi in 17th- century Prague, discusses the famous question as to why the Torah is not explicit that the revelation took place on Shavuot, in his commentary Kli Yakar. He finds a hint to the giving of the Torah in the instruction to bring a minchah chadashah, a “new offering” on Shavuot.

Rabbi Luntschitz tells us that this new offering is the Torah itself. The essence of Torah is chiddush, the new insights and meanings we have to develop to keep Torah relevant and powerful. If we can do that with cheesecake, we can do it with anything, and that is the key to our spiritual endurance.