Many years ago I took a “professional basics” cooking class from a chef, Eberhard Werthmann, and he gave me some good advice about the importance of correctly calculating the amount of food you need to feed a crowd.

“Never ask a butcher how much meat to buy,” he said.

Too bad our legislators never took a class from Werthmann. Not only would they be better cooks, they’d be better legislators.

The tip came back to me in recent days as I’ve watched them squirm over how to come up with the cash to fund the Vikings stadium, now that it’s becoming painfully obvious that the electronic pulltab gambit isn’t working and may never work.

As this newspaper has uncovered, elected officials including legislators from both parties, Gov. Mark Dayton and his appointees all relied heavily on the gaming industry to provide estimates on how much the state could raise to pay for the stadium. As luck would have it, the gaming industry gave the elected officials the number they needed to sell the stadium.

Surprise! They asked the butcher how much meat to buy and he sold them too much meat.

Then Monday it was announced that, “after being in the field,” the much touted electronic bingo games are on the fritz, and have been pulled back for repairs.

Ladies and gentlemen, clear your cards.

For the past year, officials pushing the stadium have backed the numbers. Minnesota Revenue Commissioner Myron Frans, among others, called the $34 million guess “a very reasonable and conservative estimate.” His confidence, “on a scale of 1 to 10 … it’s above 5, probably 8.”

Not everyone bought it.

Sen. Sean Nienow, R-Cambridge, said it was “based on a wing and a prayer.”

“There was nothing to base it on,” said Nienow. “It was willful blindness.”

He said many legislators, even those who voted for the stadium, admitted “in the shadows” that it wouldn’t work. “They thought it would come closer, that they were mostly right. Now, they are mostly wrong.”

Former Sen. John Howe, R-Red Wing, predicted more than a year ago that “there will be an I-told-you-so moment” about gambling projections.

Howe lost his election, but refused to gloat because the miscalculation “will lead to added taxation, and not on the people who use the stadium.”

Asked why so many people accepted the numbers, Howe said: “Fear is a terrible motivator.”

Howe also said funding decisions were made in secret. “How is it the conference committee report was done before the conference committee met? There was no input.”

You can find other skeptics of the gambling numbers easily “in the field,” by which I mean Elsie’s Restaurant, Bar and Bowling Center in northeast Minneapolis. (Someone had to do the field work.) It is one of just four Minneapolis bars with the machines.

Monday night I sidled up to the bar and asked a busy bartender if they had e-tabs. He said he’d get the machine, then dashed off to make more drinks. About 5 minutes later, he returned with the machine. I hit the “help” button for instructions.

It said: “See bartender.”

Meanwhile, two women behind me playing paper pulltabs had gotten their second basket of tabs, designated for a charity NOT the Vikings.

About five minutes later I flagged the bartender for instructions. I had to pay him, and he went back to a computer to let me into the system.

I quickly spent my five dollars on five games, one of which my wife called “the androgynous pirate one.”

The women were chatting and laughing over the paper tabs, while I stared at my computer and waited for the bartender to return for more money.

I finally asked the women why they weren’t playing e-tabs.

“They have those here?” one asked.

The women said they prefer paper tabs because “we do it together,” and because they have developed rituals around the tactile feel of the little tickets. For example, when they find a winner, they place it under their rear ends to “keep it warm.”

Can’t do that with a computer.

Tim Tuttle, owner of Elsie’s, stopped by. He said the first few months, the bar actually lost money on the games, and that paper tabs still make up 90 percent of his sales.

Tuttle pulled up his sales for March. Gamblers had paid in just over $5,000 to e-tabs and had won back about $4,800. So Elsie’s had contributed just $200 to the stadium while paper sales soared?

“That’s right,” said Tuttle. “They haven’t helped the business at all, and they are a headache for the bartenders.”

Meanwhile, some legislators are suggesting a tax on drinks, which will be another headache for bar owners like Tuttle. All because a lot of overly eager officials asked the butcher how much meat to buy.

I noticed a sign at the bottom of the e-tab machine. It said: “If playing isn’t fun any more, call for help.”

It might be time for public officials to look up that number.