But her publicists had disappeared. She gave the samples to her driver, seated in a black S.U.V. “We’re trying to convert people to the vegan way,” she said.

“I’m already a vegan,” he said, nibbling politely.

Ms. Coolidge flounced back into the store, where Ms. Vargas flourished a new treat: a whipped cream made from coconuts. A self-professed whipped cream enthusiast, Ms. Coolidge’s bedroom eyes went avid and wide. “Let’s try it,” she said, shaking the bottle with vigor. Before she could spray it right onto her fingers, Ms. Vargas brought over paper cups.

“This is delicious,” she said, her voice deepening to a purr. Ms. Vargas offered her a swirl of the store’s vanilla soft-serve ice cream, and Ms. Coolidge sprayed more whipped cream over the top.

“This couldn’t be any more fun,” Ms. Coolidge said. “People’s idea of vegan is, like, kale.”

Though she splits her time between Los Angeles and New Orleans, she has been contemplating a move to New York, where she lived and waitressed in the late 1980s and early 1990s. The soft serve confirmed it.