How to Frost a Square Cake with Buttercream~Video

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Today, I'm going to show you how to cover a square cake with buttercream! I hope that you'll find a tip or two in the tutorial that will make the process much less intimidating.


The truth is, frosting a square cake with buttercream is not difficult if you have a good method-- but it is definitely more time consuming than frosting a round cake.  There's just no way around it (and so charge accordingly if you have a cake business!)  

The more that you practice frosting square cakes, the more quickly things will come together--and if you follow the steps in this tutorial, you will be impressed with your square-caking skills in no time!

Make sure to check out additional information beneath the video--enjoy!




Details about our Square Cake

In this tutorial, I'm frosting a three layer White Almond Sour Cream (doctored mix) recipe-- These are six inch cake layers.  They have already been filled and settled prior to the start of the video.

Buttercream- I used our High Ratio recipe.  I like crusting buttercreams and so any of ours would work well (High Ratio, Fluffy Vanilla, Classic Vanilla...).  If you do not work with crusting buttercreams, you will still be able to use the most important tips in this tutorial--but you will not be able to use the Viva Paper Towel method for smoothing, as I do in the end.

Foam Core Board slightly larger than your cake-- My board was about ¼ inch larger than my cake on all sides.  A thickness of ½ inch is a good choice.  The thicker boards are less likely to bend under the weight of your cake when you move them, and it's also a good thickness for guiding your bench scraper.

Bench Scraper- I like a bench scraper with a curled handle like THIS ONE.  It doesn't have to look exactly like this, but it's best if the handle doesn't extend past the edge.

Pot of Hot Water -- * With Swiss Meringue buttercreams, very hot spatulas can cause color streaking--so, do a test patch on a plate to be sure. If your color streaks, skip the hot knife step (but you can still chill your cake in between frosting applications)

Viva Paper Towel- Optional, but I like the "Viva Method" as a finishing touch

Fondant Smoothers- Again, optional--but if you are using the Viva Method of smoothing for final touches, they are helpful

Miscellaneous~  I used a piece of food safe vinyl to cover my countertop (optional) to keep things clean.  I used a larger cake board to transfer the cake to and from the freezer.


 Notes for Frosting Square Cakes

As I mentioned in the video, the most important part of the method is that you are using your cake board as your guide, as well as a bench scraper.  

If your usual smoothing methods don't match mine, that is fine.  You can experiment with other ways of frosting your cakes--but I think that you'll find that using a slightly larger board than your cake will help you to achieve those sharp corners even if the cake itself doesn't have corners as sharp.

You will want to make more frosting than you will actually need.  You can freeze the leftover frosting in an airtight container.  

The reason for the excess is that you will want to really build out your frosting, just past the cake board, so that when you go back with your bench scraper, the scraper will be in contact with frosting from bottom to top.  Once that excess is scraped away, you'll be left with a very smooth and even layer of frosting.

* There are other great methods out there for achieving sharp corners, and I encourage you to experiment with as many as you can.  

Cake decorating is all about finding what works best for you.  This is what works best for me!  I did not invent the method of using the board as a guide, and many of you will be familiar with it already--but for those who aren't, I hope that you'll give it a try!   Let us know how it goes ;0)

**(You can now purchase re-useable acrylic squares or circles for this method!)



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  1. Is there a place to order/buy the foam core board squares already cut to size you need? Afraid I will cut it and then that won't be square! LOL

  2. Hi Leane, this is a link to a site that will precut foam core to size, I would have the foam core be 1/4 to 1/2 inch thickness.

    Also, anywhere that does framing has foam core and you could buy a sheet and have them cut you as many sizes as you would like from that one sheet.

    Remember that your cake always shrinks a bit so keep that in mind when deciding the size of your square board. I don't like a think layer of frosting, so when I am frosting a buttercream square cake, if it is a 6 inch cake my board is cut to six inches and with the shrinkage it is enough frosting for me.

  3. Thanks so much! I was just thinking of me cutting foam board and the disaster that would follow! LOL Did not even think of a frame shop!

  4. Leane thanks so much for your question, and BeBe thanks for the resource. I was wondering about this at well.

  5. what brand of square pans do you use? how many people would a square cake feed if im doing 2 tiers... one 9 inch tier and one 6 inch tier with three layers each?

  6. This is a great video Melissa and BeBe. I wish I had watched it prior to making the rainbow birthday cake in the rectangle shape which I posted a photo of in the "children's" category. I had a heck of a time getting the edges sharp...they weren't exactly, but did look ok :-/ Next time I make a rectangle cake I will use my bench scraper as I think your method would also apply to rectangles. Great video. Thank you.

  7. I bought a couple of sheets of foam core board from Michael's. It is Elmer's Brand. When we cut it the foam wrinkled and pulled on one of the sides. Could this be filled in with RI?

    I am making 8-10 inch square cakes for my son's wedding in August. Thanks so much for the timing on the tutorial. I am practicing a lot, since caking is a hobby for me, everyone gets square cakes til August.

  8. Hi Sandy, I think that it could still be fine as it is. As you build out the ganache, if that is what you will be using I think that will fill in the rough edges and you should still be able to smooth with your bench scraper. The royal icing is a good idea but I think it would be fragile and break as you scrape, though I'm not sure. Let us know how it goes.

  9. This video just proves that I have to increase my level of patience. That's my problem, I never take all the time necessary. I find that I rush to get it done and it's never this good :)

  10. Hi Mimi-- Yes...patience is key! ;0) Honestly, I do not always make my cakes with razor sharp edges- mine often have a softer look. But, since we see more and more of this look in cake land, I wanted to demonstrate how to do it! The most important thing is to remember is that square cakes are not only more servings than round, they take about twice as long to frost or cover. So, make sure to charge more for squares!