Herein lies the magic behind “My Fat Dad.” Despite her parents’ frustrating attitudes toward food, Lerman absorbs eclectic food secrets everywhere she goes, preserving a sense of innocent curiosity while developing a bold palate. Readers will enjoy more than one “aha!” moment when Lerman’s correspondence and conversations with Grandma Beauty in Chicago reveal traditional Jewish cooking secrets: schmaltz and ginger ale, for example, will keep a matzo ball from becoming “hard like a baseball.” Likewise, Lerman exposes lemon juice to be the key ingredient binding together a noodle kugel.