The cook at Sutter’s Fort, an Englishman, promised he could produce a Christmas dinner “that would rival Delmonico’s best efforts.” (Delmonico’s Restaurant in New York City being the epitome of fine dining.)

A banquet at Delmonico’s, not to be confused with dinner at Sutter’s Fort. From Wikipedia.
He also promised to top off the whole affair with “a dessert consisting of a real John Bull plum pudding.” It sounded irresistible, but where was he to get the necessary ingredients?
As our author notes, the cook had no spices, no butter or milk or eggs. The only fruit he had was the little sour grapes that grew along the river banks. How could he make a real plum pudding?
After five courses of variations on beef and chile colorado, the diners were ready for relief to the rumbling stomachs. It was time for that crowning achievement, the plum pudding!
He brought it in with an air of great self-gratulation, and such a pudding! It is doubtful if another, to compare with it, has ever been or ever will be concocted. In its construction the cook had used common beef tallow liberally, and filled it with the aforesaid sour grapes, and seasoned it unsparingly with chile colorado, black pepper, salt and garlic. He also made a sort of sauce with the panoche sugar and tallow, and had also dosed that liberally with chile and black peppers.
The pudding was served to the diners, and they all watched as Captain Sutter tasted his portion. Captain Sutter was a man of the most courteous manners, and felt it his duty to eat whatever was put before him. But this dish bothered him.
As he would gulp it down, he would look around at us, with a sort of dazed and helpless look, evidently to see if we were really eating it, and how the thing was affecting us. But he was too well bred and dignified in bis manners to say a word.
Poor Captain Sutter! At last another man asked “Cook, what is it?”
“Why, sir.” replied the cook, “it is a regular Christmas plum pudding, Mexican style!”
And so ended Christmas dinner, 1845, at Sutter’s Fort.
Note: The author mentions “panoche” sugar. This is unrefined Mexican brown sugar, formed into a cone, and also known as piloncillo. You can buy it in most grocery stores. “Unbolted” flour is coarse, unsifted whole wheat flour.