In 1819 Moritz Schlesinger, son of the founder of the Berlin publishing
house Adolf Schlesinger, traveled to Vienna to visit Beethoven. He caught
up with him at the composer's summer residence at Mödling, and years
later wrote the following anecdote about his meeting.

"After getting out of the wagon I went to the inn and found Beethoven
there, who came out the door in a fury and slammed it hard behind him.
After I had dusted off a bit I went to the house which was designated
as his dwelling. His housekeeper told me that it would be better not to
speak to him as he had returned home in a rage. I gave her my visiting
card which she brought to him, and after a few minutes to my great
astonishment she came out again and bade me enter. Inside I found the
great man at his writing desk….He let himself go momentarily and told
me that he was the most miserable man in the world; a minute ago he
came out of the inn where he had asked for a piece of veal which he
specially desired but there was none left — all this with a very
serious and dark expression. I comforted him; we spoke (I always
writing)* of other things and so he detained me for two hours…After
leaving him I hurried back to Vienna in my wagon and asked my inn boy
if there were any veal available. Upon finding there was I left it on
the platter, well covered up, and, without writing a word, I gave it
to the man waiting in the carriage to take to Mödling and present to
Beethoven in my name. One morning soon afterwards I was still lying
in bed when in came Beethoven, who kissed and embraced me and said
I was the best fellow he had ever met; never had anything made him so
happy as this veal for which at that moment he had had such a longing."

You never can tell what is going to make these genius artists happy.

During that year Beethoven finished less than a handful of works, none
of which today bear opus numbers. So what was he working on during
that period? He was composing the Missa Solemnis — "singing, howling,
and stamping" parts of it as he composed to the great annoyance of his
neighbors and the great concern of his friends. So I guess that veal
produced a good result. In an odd sort of way.

*Into one of Beethoven's "conversation books" that he kept due to his

Source: Forbes, Elliot ed., Thayer's Life of Beethoven, Princeton 1970.