I have heard in the name of the Chasam Sofer that if one sleeps after eating meat that they can be lenient in the amount of time one would normally wait between eating meat and milk. Is this written anywhere? Which other poskim discussed this?
The sefer "Zikaron L'Moshe" (pg. 65) writes that the Chasam Sofer originally understood that the reason one must wait six hours after meat, is because that is how long it takes to digest the food, and therefore this only applies to one who ate a meal in the day. However, when one sleeps the food digests quicker, and he may eat milk even before six hours are up. Based on this reasoning, the Chasam Sofer prepared himself a cup of coffee to drink, but when he picked it up the cup broke and the coffee spilt, which the Chassam Sofer took as a Divine sign that he was incorrect and the full wait time applies even after sleeping.
I heard that Rav Elyashiv zt"l held this way, and that it was halakha l'maaseh for him because he slept for less than six hours.
Rav Eliyashiv (Ashrei HaIsh page 45:25 held that if one slept for 3 hours one can eat chicken right away. However ,he notes that this leniency only applies to chicken and a sleep during night time. This would not work for meat of a beheima. He adds ,that if one ate hard cheese one can rely on this leniency even if they slept during the day time.
Text of Ashrei HaIsh: