After the two stars left Seyfried's home (which she shares with older sister and personal assistant Jennifer), they went grocery shopping at Trader Joe's, where they picked up yogurt, tortilla chips, cereal, bread and juice. See more photos of the hot new couple at X17.
One night earlier, Seyfried and Hartnett met up with friends at West Hollywood's Chateau Marmont. At one point, Seyfried "sat in Josh's lap with her arm around him, and took his knit hat, placing it on her head as she looked at him," an eyewitness tells Us of the affectionate duo. "Josh seemed considerate and Amanda really seemed to be loving the attention and looks he gave her."
Hartnett isn't the first A-list actor Seyfried has romanced; the Gone star's previous loves include Dominic Cooper, Ryan Phillippe and Alexander Skarsgard.
In 2011, Seyfried shared her dating dealbreakers with Glamour UK. "Poor hygiene is an absolute no-no: they have to shower once or twice daily at least," she revealed. "Oh, and I could never be with someone who treats his mother like sh-t, or a guy who waxes his chest."