10/21/2012 at 02:00 PM EDT
and husband Geoffrey Arend
visited the House of Walker in Los Angeles on Thursday night.
The Emmy nominated Mad Men
actress – who is a Johnnie Walker Scotch Whisky Ambassador – wore a black satin Temperly London dress and jewels by Tacori. Much to the surprise of guests, Hendricks was there to lead a Black Label tasting and guided a group through the ins and outs of whiskey.
Once the tasting was over, Hendricks and Arend sat in a VIP area with a group of close friends.
"Christina was overheard saying that she is back to work on the set of Mad Men
next week and just received the script for the first episode the night before," an onlooker tells PEOPLE. "She's excited to see what happens to her character this season. Christina's grown to love Joan over the years and as a fan of the character, she only wants good things to happen to her."
After a fun evening, Hendricks and Arend left House of Walker around midnight.
"She said she was heading to Koreatown for a midnight snack!" the source adds.
– Melody Chiu