SHEFFIELD, England — Come January, everyone’s an expert on what you should, and should not, be eating, and in what quantities you should, and should not, be eating it.

Not Ruby Tandoh, who is standing in her kitchen in South Yorkshire, sizzling plantains in an inch of oil until they’re a deep brown all over and tender inside.

Ms. Tandoh, a 24-year-old food writer with a cult following in Britain, doesn’t endorse a set of rules by which you should shop, cook and eat. Instead, she champions the miscellaneous delights, the quiet quotidian pleasures, of cooking without rules.

“I can hear the voices of aunties in my head,” she said, sliding across the linoleum to flip the sputtering plantains. “They’re telling me not to overcrowd the pan.”