From: Rabbi Akiva Eiger
To: Unknown recipient
The question is whether fat left unsalted for three days is subject to the same prohibition as meat under Yoreh Deah 69. Rabbi Akiva Eiger sides firmly with the Pri Megadim against the lenient ruling of the Shevus Yaakov, finding the Shevus Yaakov's proof unconvincing, and bolsters this stringent position by citing the Noda BiYehudah who likewise rejected the leniency.
Source: Shu"t Rabbi Akiva Eiger §44