Great question — answering as the UphillTech team:
According to the script it’s butter that has not set (from a "butter mold"). Slow track towards the kitchen table - ROSE brings the butter mold to the table, as the two SWEDISH KIDS (from the trading post, then Payne’s gang) play by the table ROSE lifts the lid of the butter, but it still has not set and flows onto the table
Full answer by Pam: https://movies.stackexchange.com/a/110272 (CC BY-SA 4.0).
Need it done for your business? UphillTech.
