Growing up in California, 27-year-old Melissa Ng loved eating the foods her mother's family brought from Indonesia.

With her grandmother now in her 90s and her aunt on a health kick, some of Ms. Ng's favorite family dishes—nasi goreng, a fried rice, and beef rendang, a beef-and-coconut curry—are rarely served. And food at the Indonesian restaurants near her home in San Jose "always seems blander," she says.

To...