Do you really find it hard to imagine that Trump wants extra? And that he gets a custom menu instead of eating what everyone else does? It's not really important enough to investigate, but:
The waiters know well Trump’s personal preferences. As he settles down, they bring him a Diet Coke, while the rest of us are served water, with the Vice President sitting at one end of the table. With the salad course, Trump is served what appears to be Thousand Island dressing instead of the creamy vinaigrette for his guests. When the chicken arrives, he is the only one given an extra dish of sauce. At the dessert course, he gets two scoops of vanilla ice cream with his chocolate cream pie, instead of the single scoop for everyone else. The tastes of Pence are also tended to. Instead of the pie, he gets a fruit plate.
These were first hand observations by Time magazine reporters, not a leak from a whistleblowing waiter.
It would be funny if he were in the UK and they didn't let him have any ice cream.