For this Lego cake I used a mini loaf pan and make as many pieces as you need. Cut the top off each loaf as you want these to be square. Make whatever color icing you want.
Ice each cake making them quite smooth. Ice some mini marshmallows for the tops of the Lego pieces. You may have to thin the icing to get it to stick to the marshmallows.
For my son’s tenth birthday I wanted to make a lego cake to go with his favorite toys -Star Wars Lego’s. Together he and I made the characters and vehicles out of fondant. The cake is iced in buttercream. The Lego "bumps" are homemade circular cutout cookies sandwiched with buttercream and iced into placed.
My son has always liked legos so I wanted to give a lego cake it a try! As you can see it is a bit rough around the edges (working on little sleep!) but he was very thankful. I used bread pans that were only filled a 1/4 or so. I iced all the pieces with a standard butter cream that was white (didn’t want to mix the colors!). Since I had very little time I cheated and used the "spray icing" in primary colors. I stacked the legos then added the circles with just a round of icing that I smoothed out. By the way, the green cake board was just green contact paper that happened to be the right color covering a piece of oak.