We like surprises, but rarely when it comes to what we eat. Amanda Rettke’s cakes might change that attitude.

Her cakes look conventional — until you cut a slice, revealing the surprise shape inside. It could be a bumblebee or a football, a candle or a pair of cherries. She makes cakes that conceal rainbow hearts, engagement rings, or bunny faces, all rendered in cake and frosting that she’s cut out, doctored and reassembled.

A surprise-inside cake is the culinary equivalent of a ship-in-a-bottle. How does she do that?

Now, her step-by-step (and let’s be honest: by-step-by-step) techniques are revealed in “Surprise-Inside Cakes” (William Morrow, $30).

With the almost 300-page book chock-full of color photos, Rettke joins the rarefied league of food bloggers whose work attracted the attention of a publishing house, and for whom the intangibility of the Internet now comes to Earth in a 2.2-pound book.

Rettke, who lives near Bethel, said her journey began 10 years ago when she had her first child and started a blog called “i am mommy.”

“It wasn’t even called a blog, really, back then,” she said, but something she did through a journaling website. More kids arrived; she and her husband now raise five, the youngest at 9 months old.

“They kept being born, and having birthdays, and we had more functions to go to where you’d bring cake or cookies,” she said. “But I’d literally never baked anything in my life.”

A Martha Stewart episode about decorated sugar cookies inspired her and she dived in, realizing that she not only could make them, but enjoyed it. Still, with more kids underfoot, she found it more challenging to tackle the intricately piped frosting designs, and switched to baking cakes.

In 2010, she started another blog, “i am baker,” joking that people found it “far more interesting” than her mommy blog.

Today, “i am baker” has 12,000 subscribers, and averages 2 million page views a month. Her desserts have been featured on “The Martha Stewart Show,” in Brides magazine, and she’s an online cake instructor for Craftsy.

A big reason for that success is her surprise-inside cakes.

Her first was a heart-inside cake, which she figured out by trial and error. “Then someone told me that Wilton sells a pan that does that,” she said, laughing. “So the premise was out there; I just hadn’t been exposed to it. But all of my surprise-inside cakes in the book are original in that I created the technique for how I do it.”

How does she do it?

For starters, she wakes up two hours before the rest of her household, and before home schooling begins for the day. The shapes often involve cutting or scooping out portions of a baked cake, crumbling that, then binding the crumbs with buttercream — much like making a cake pop — which enables her to form the shape. Reassembled and frosted, the interior remains hidden until the first slice is removed.

The recipes range from easy to challenging, with the easiest being interiors that are striped or swirled instead of featuring shapes.

Producing the cookbook was a huge effort, given the need for clear step-by-step photography, all of which Rettke did herself. The “beauty shots” of the finished cakes were done by a professional, Susan Powers.

Many of the cakes are based around a sturdy white cake recipe that calls for five egg whites. With some recipes calling for three batches of cake, that’s a lot of spare egg yolks, but she said that they freeze beautifully, and noted that she’s now becoming a big fan of yellow cakes.

Rettke, 37, said she often refers to herself as “a still learning baker.” In fact, she is working on a second book, but exploring a new method of interior interest that involves cutting shapes from a baked cake, then placing them in more cake batter to bake again.

“It’s a method that lends itself to more opportunity in other designs,” she said. “And it tastes really good.”

That should come as no surprise.