The Jewish springtime Passover holiday is known as a festival of freedom, but its hallmark is a litany of dietary restrictions centered on not eating leavened bread for a week.
The rules are so elaborate that chefs who want to observe the ritual law must prepare weeks before, removing every last crumb, buying up new sets of kitchen utensils and planning menus without bread or wheat flour.
In the suburbs, Jews' preparations for Passover culminated in a holiday dinner Friday known as the Seder.
As families gathered everywhere, Chabad of Naperville held a Seder Friday for the public. And Congregation Or Tikvah in Grayslake prepared Friday to hold their Seder meal Saturday evening for around 50 people.
In Israel, preparations can be elaborate.
At Liliyot, one of Tel Aviv's most prestigious kosher restaurants, chef Noam Dekkers oversaw his staff on Wednesday, their last regular day in the kitchen before the annual Passover scrubdown -- a process he calls "logistical mayhem."
At the end of the day, Dekkers' cooks threw away leftovers like chopped vegetables and fish. Then, they stored plastic cutting boards and boxes, locked grains away and scrubbed all steel cooking ware.
The following morning, city rabbis oversaw the final sterilization, when the restaurant staff blowtorched grease off the grills and dunked all the metal and glass cooking utensils into caldrons of boiling water. As of Thursday night, Liliyot was kosher for Passover.
"Tel Aviv is a secular city," said Dekkers, a nonobservant Jewish Israeli. "But quite a big part of the community keeps the Jewish religious traditions, especially of the holidays."
The preparations at Liliyot are part of a nationwide frenzy as Jewish Israelis prepare for Passover with a binge of cleaning and shopping culminating in a holiday dinner Friday known as the Seder.
The holiday began Friday at sundown, and a horn blasted over a system of loudspeakers through the empty streets of Jerusalem's Jewish neighborhoods to alert residents that Passover has started. Earlier in the day, thousands swarmed into the city's cavernous Mahaneh Yehuda market to stock up on food.
Passover celebrates the biblical Exodus story of the Israelites' escape from slavery in Egypt.
God killed the firstborn boys of Egypt after the pharaoh refused to release the children of Israel from bondage, but "passed over" the houses of the Israelites. Distraught over losing his son, the pharaoh let the slaves free, and the Israelites fled so quickly they did not have time to wait for their bread dough to rise before baking it.
So on Passover, observant Jews avoid bread and instead eat thin wheat crackers called matzoh to recall the Israelites' flight.
Beyond the injunction on bread, observant Jews also refrain from eating grains like wheat, spelt, rye and oats on the holiday unless they're in the form of matzoh. And Jews whose ancestors come from Eastern Europe also steer clear of legumes and rice.
The Passover rules are in addition to regular kosher regulations that proscribe pork, require meat to be ritually slaughtered and forbid mixing of meat and dairy.
In Tel Aviv, about 950 businesses keep kosher year-round. Rabbi Shimon Baluka, director of the Tel Aviv-Yafo Rabbinate's kosher department, says the Passover rules are so tough that only a third of the kosher businesses take the trouble to get certified. The others close for the holiday.
Besides the pre-Passover inspection, about 100 supervisors will ensure kosher restaurants abide by the rules during the holiday, Baluka said.
At Liliyot, beyond cleaning, keeping kosher for Passover means stripping the regular menu of any chametz, the catchall word for food not kosher for the holiday.
Dekkers said he changed his menu while trying to hew as much to the original as possible. For example, seared gray mullet served over black radish and a slice of chewy focaccia becomes kosher without the bread. The juicy rib-eye steak served with multicolored carrots is nearly untouched. Pasta dishes are gone.
The most important thing, Dekkers said, is to keep the food light with plenty of interesting produce.
"I don't have a problem with heavy food, but I do have a problem with that heavy feeling after a meal," he said.
Passover is the holiday most celebrated by Israeli Jews, according to a 2009 survey on religion conducted by the Israeli Central Bureau of Statistics.
Even though only about 20 percent of Israeli Jews identify themselves as Orthodox, almost everyone attends a Seder. And two-thirds of Israeli Jews refrain from eating chametz throughout the weeklong holiday.
To accommodate them, the Israeli food industry transforms. Snack manufacturers replace regular flour with matzoh meal. Cows eat corn and alfalfa instead of hay to prevent a stray grain of chametz from getting into milk. And supermarkets cover up non-kosher products with large sheets, meaning regular breakfast cereals and crackers will be hard to find.
For some, the rules can be liberating.
Pastry chef Avi Melamedson makes yogurt mousse, poppy cake and a flourless chocolate fudge on the holiday.
"I have placed a kind of veto on matzoh meal," Melamedson said. "You can use great raw materials and get quality products without flour."
Janna Gur, founder and editor of the Al Hashulchan (On the Table) food magazine, said that in contrast to more adventurous years, Israeli home cooks are currently focusing on their own family recipes from around the Jewish world.
"People got tired of trying to reinvent themselves with a completely new Seder, and they are going back to tradition," Gur said.
Because the Passover holiday is so sacrosanct in Israel, even bucking it takes special preparation.
Liar Hargil owns the Minzar pub in central Tel Aviv. It is one of the few establishments that will remain open on Friday night, when most Israelis will be eating the Seder meal.
Hargil said he orders beer, which is not kosher for Passover, three weeks before the holiday, holding 200 kegs in a neighboring convenience store to take him through seven days when he cannot fill his taps. He freezes loaves of bread because most bakeries are shuttered, and stockpiles flour because most of the supermarkets nearby won't sell it.
"I want a sense of order and a vacation and not to have to run around," he said. And among secular Israelis, he said, "People actually want extra chametz."