Bentley Gets a Birthday Cake

Bentley tastes his birthday cakeFor his 16th birthday I decided it was time to make a cake Bentley could eat.  There would be no more watching as the humans ate birthday cake and he didn't get any.

Bentley eats a prescription diet that is fish and potato based.  At his last vet visit, the vet suggested we decrease the amount of dry food and supplement his diet with mashed potatoes. The potatoes increase the amount of easily digestible carbohydrates and are easier on his digestive system. That gave me the idea that a doggy-edible birthday cake could be made of mashed potatoes.

Potatoes are approved by Bentley's vet as part of his regular diet. If you have concerns about feeding potatoes to your dog, check with your vet and use only foods that are safe for your dog.

How to make a doggy-edible birthday cake

In the photo above, I'm holding a 12" by 16" cutting board. The cake is about 3/4 inch thick. 

Supplies & Ingredients

  • A large, flat surface that the mashed potatoes won't stick to. It's not visible in the picture but I have a thin, flexible plastic cutting board on top of the wood cutting board.  The back side of a baking tray would also work.

  • A box of instant mashed potatoes. The generic brands work fine.  I used about 5 cups of potato flakes for this cake (I buy 28 ounce boxes because Bentley eats potatoes as part of his regular diet). 

  • Water

  • Decorations. 
    Healthy doggy-edible decorations might include things like dry dog food, carrots, peas, cheerio-type cereal, or corn flakes. You can also crush the decorations to sprinkle them on the cake

    Hints: 1) The drier the decorations the better because a "wet" decoration will seep into the white potatoes. Something like fruit or berries probably wouldn't work very well. 2) The decoration needs to firm enough so you will be able to push it into the cake a little it so it doesn't fall off. 

  • Food coloring if you're going to make potato frosting

  • A large bowl to mix the potatoes in (for the cake part)

  • Plastic food storage bags  - one for each color of potato "frosting" (if that's the way you're going to decorate).  I used gallon and sandwich sized bags.

  • Scissors - to cut a little hole in the plastic bags.


  • Do not follow the directions on the box of potatoes. Do not boil the water and DO NOT add salt, milk, or butter. 

  • In a large bowl mix about 3 cups of instant mashed potato flakes with about 3 cups water.

  • Mix thoroughly, adding more water (or potatoes) as needed to get a consistency wet enough to be moldable, yet firm enough to hold a shape.

  • Put the mashed potatoes on the large, flat surface and shape them into a cake about 1/2 inch thick.  
    The thickness doesn't really matter, it just has to be thick enough to hold the shape without cracking. 

  • Wet your fingers to smooth out the surface and prevent the potatoes from sticking to your hands.

"Potato Frosting"

  • Squeezing the potato frosting onto the cake. Estimate how much potato frosting you'll need based on the size cake and how much decoration you want.

  • You want the frosting wet enough to squeeze out of the plastic bag, but not so wet it's runny. 

  • Use a bag large enough that you'll be able to zipper or twist the top shut.  You will squeeze the potatoes out of a hole you cut in the bottom corner of the bag.

  • Mix food coloring into the water before you add it to the potato flakes. That will help make the potatoes evenly colored. It takes a generous squirt of food coloring to color the potatoes, so make sure the water is intensely colored.  

  • Put potato flakes in a plastic food storage bag, then add the colored water and mix.  Add enough colored water until you have the potatoes a squishable consistency, but not runny.

  • Zip close or twist & hold the top of the bag tightly shut.

  • Cut a small piece off the bottom corner of the bag, then squeeze the potatoes into that corner of the bag and squeeze the potato frosting out to decorate the cake.

  • You can wet your fingers to smooth out the frosting on the cake.

Serving & Storage

  • After Bentley tasted his cake, I removed all the colored potato frosting and threw it away.  The food coloring is probably safe to eat, but he has a sensitive digestive system and I didn't want to risk upsetting it.p

  • The uneaten portion can be refrigerated for 3-4 days. 

  • You'll be ruining all your work, but put the leftovers in a food storage container. A little of the water tends to separate out of the potatoes after a day in the fridge, and you'll have a mess if it's not in a container. 

Bentley's 17th birthday cake

This year I used mostly dry dog food to decorate his mashed potato cake. Just push the decorations into the potato cake a little bit so they don't fall off. The orange decoration is from a tube of human-edible icing, which I did not allow him to eat. 

Hint: these icings are usually a little runny and will "bleed" into the cake. So if you have cake decorating supplies (the little tips you use to decorate cakes) you can squeeze all the frosting out of the tube into a bowl, thicken it with cornstarch, then put it in a plastic bag with the decorator tip poked through the corner of the bag. Tape the tip and bag together on the outside because you'll have to squeeze really hard to get the thickened frosting out and you don't want the tip to push through the bag. 

Remember - if the cake isn't perfect, your dog won't care!  Just be safe and have fun.