Whoopie pies, the sweet specialty cakes once not widely found outside of New England and Pennsylvania, are suddenly hip and spreading from coast to coast.

Bakeries around the country are developing all sorts of gourmet versions of the yummy confections. Instead of the classic cream-filled chocolate cakes that have put a gooey smile on so many faces, bakers are experimenting with flavor combinations such as Meyer lemon with a ginger creme and sour cherry with white chocolate filling.

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Nancy Griffin's "Making Whoopies: The Official Whoopie Pie Book" explores the rise to trendiness of the chocolate-and-cream-filling treat.

Whoopie pies also appear to be de-throning cupcakes as the king of trendy snacks, even in Europe. Harrods in London, according to news reports, has had to hire extra bakers to keep up with the demand.

If you want to impress your out-of-state friends with your knowledge of whoopie pie lore, pick up a copy of “Making Whoopies: The Official Whoopie Pie Book” (Down East $12.95) by Nancy Griffin.

The book explores the origins of the snack and offers 16 recipes, including tempting versions from Isamax Snacks Bakery in Gardiner, the Eastwind Inn in Tenants Harbor and Two Fat Cats Bakery right here in Portland. Want a healthier option? There are recipes for a gluten-free whoopie and a lower-fat zucchini whoopie that replaces butter with canola oil and mixes cottage cheese into the cream cheese filling.