Pimm’s Cup
Season 1, Episode 4, “Anastasia” (2010) · Senator Walter Edge and Nucky Thompson
At Nucky's birthday party, Senator Edge orders a Pimm's Cup, is told the house is out, and uses it to say you can't have everything; the next day Nucky sends him Pimm's with a note saying he does expect to have everything.
Sources: Wikipedia - Anastasia (Boardwalk Empire); The A.V. Club - Boardwalk Empire: Anastasia; Seattle Met - Pimm's Cup and Boardwalk Empire