I'm making a lego cake and I want to build the blocks up the sides of my square cake. In order to this, I was thinking that I should let the fondant harden slightly before sticking them to the sides of the cake, so that they keep nice hard edges.
1) How long should I leave the "bricks" our to harden before applying them to the sides of the cake if I don't want them to get too hard, as they are not purely decorative.
Use modeling chocolate if the cake will be indoors!! http://jessicakesblog.blogspot.com/2013/06/lego-cake.html
That link has the best lego cake, and she used modeling chocolate to get really clean sides. Modeling chocolate has changed my decorating life. Also, she has a Craftsy class that is 50% off from her blog. It was well worth the money! You will get the cleanest lines ever!
I'm do you think that the modeling chocolate will taste good? im trying to make smaller "real life" lego sized blocks to put on the side - kind of like this cake: http://farm7.staticflickr.com/6188/6150827638_b8dc7fe921_z.jpg
So i'll have to be able to cut into it.
The modeling chocolate tastes way better than fondant! I have used both wilton melts, like Jessicakes, and white chocolate apeels. It tastes like white chocolate, just softer. I can't stand the taste/texture of fondant, but I use it because sometimes I have to. But modeling chocolate will work for the cake in your picture. It'll taste great.
ok great! last question - should i get white and dye them myself of try and find colored ones?
(will the dye mess up the consistency of the white chocolate)
Jessicakes uses pre colored ones, Wilton brand, and she alters the colors if needed. I usually use white chocolate, but it is important that you add the color to the corn syrup before adding it into the chocolate. Also, don't overmix. The color of the corn syrup will obviously lighten when mixed with white chocolate. Read jessicakes' blog post about how she makes her modeling chocolate if you haven't already. I believe you can add color after the chocolate has rested if you didn't get the desired color.