Related על פסחים 10:8

We may not eat an afikoman [a dessert or other foods eaten after the meal] after [we are finished eating] the Pesach sacrifice; for example nuts, dates and roasted wheat. A man is obligated to be involved with the laws of Pesach the whole night, even if it [is only a discussion] between him and his son, even if it is between him and himself, even if it is between him and his student. It happened that Rabban Gamliel and the Elders were [once] reclining in the house of Beitos ben Zunin in Lud, and they were involved with the laws of Pesach the whole night until the call of the rooster. [Their students] raised the covering of the window from in front of them, and they [then] convened and went to the house of study. What is the blessing on the Pesach sacrifice? Blessed [...] who has sanctified us with His commandments and has commanded us on the eating of the Pesach sacrifice. What is the blessing on the [other] offerings? Blessed [...] who has sanctified us with His commandments and has commanded us on the eating of the offering.

And they may not conclude the Pesach meal with an afikoman [a dessert or other foods eaten after the meal], like nuts and dates and parched corn. A person must engage in the laws of Pesach all night, even if it is just him with his son, even if it is just him by himself, and even if it is just him and his student.