Sandwich mystery

We attended a wedding on Saturday, and they provided a lunch of sandwiches afterwards. While they appeared to be ordinary lunchmeat sandwiches, there was a pasty pale yellow substance on the bread, that at first was taken to be mustard by those of us at the “teen” table.

“It doesn’t look like mustard; it’s too light,” said one of my friends.

“Perhaps it is mayonnaise,” said his sister. “Or butter.”

For a moment we pondered this, and then someone got up to ask. She came back, saying with surprise: “It’s actually margarine!”

At this point, Aragorn broke in with a perfectly straight face, and said, astonished: “I can’t believe it’s not butter!”