Bake your cakes, make your buttercream and modeling chocolate a day in advance. Once your cakes are baked and cooled, wrap them in plastic wrap and chill them in the fridge so they are easier to cut.

Bake one 8? square cake (or bigger if you want a bigger cake) I used chocolate cake. You could also use vanilla cake if you wanted to do that instead.
Make one batch buttercream. I use swiss meringue buttercream because it gets nice and firm in the fridge so you can get sharp edges. Shortening based buttercream wont be good for this project
Make blue modeling chocolate. Use Lauren Kitchen’s Recipe. Add blue food color and a little black to the corn syrup (about a tablespoon or blue and 1 tsp black) to the warmed corn syrup to get the proper color.
Make 1 batch LMF white fondant for the trim and the base board.
You’ll also need two 10? cardboard rounds and some ribbon
One floral light that you can get at Joanns or online
Print out the TARDIS decals pdf (these are not edible, peel them off before you eat the cake)

Tools
x-acto knife
ceramic tools for smoothing
paint brush
food color
white food color or titanium dioxide
salt
small offset spatula
two 10? round cardboards
extra cardboard
ruler
scissors
plastic drinking straws
bread knife for cutting cake
rolling pin
bench scraper or putty knife 

Making the Board

Start off by gluing two 10? rounds together. Glue the ribbon around the outside to cover the rough edge. Roll out some of the white fondant and attach the fondant to the board with a little crisco or water. Trim off the excess fondant with an x-acto knife. Wet the entire top of the fondant with a clean, flat paint brush and a liberal amount of water. You want to create a nice wet surface to paint on.

I used this image as inspiration for my galaxy

I divided up my food color into a ceramic egg dish for ease. I added a little water to each color to thin it out. Any container will do. Even a bunch of little cups if that is all you have. I started off with yellow and worked outwards. Trying to be slightly random and not blending too much because I don’t want things to get too muddy. You can’t really do this part wrong. Just don’t over-do it.

I don’t take the color all the way to the edge though. I paint the edges with black food color straight out of the bottle because it’s nice and thick and opaque.

Sprinkle some salt randomly over the board to create little spots that look like stars. Next I take the whole thing outside and splatter some of the white food color onto the board to resemble the galaxy. A toothbrush could work for this or a big dry brush

I made this board two days in advance so that it plenty of time to dry

Making the cake
Start off by cutting your 8? square cake into four pieces. Use some of your extra cardboard to make two 4.25? square piece of cardboard. Make another piece that is 4? square. So you should have three square pieces of cardboard. Start stacking the cakes on one of the 4.25? pieces of cardboard. Put about .25? of buttercream between each layer. Don’t put too much or it will squish out.

Once you get half way through the cake. Push a plastic straw into the middle of the cake. At the point that the straw is level with the cake, mark it with your fingernail and make a cut. Measure out 3 other straws and trim to the same height. These will support the top part of your cake so it doesn’t fall over or get too compressed. Use a little more buttercream to glue the 4? square cardboard on top of the straws and cake. Continue stacking the cakes until you use the rest of the cake. I split each pice of cake in half so I had more layers of buttercream but you don’t have to do that.

Place the cake into the freezer for at least an hour until it is nice and firm so that when we add buttercream on the outside, it wont flop around.

Once the cake is nice and firm, apply a liberal coat of buttercream to the outside and top of the cake. Don’t worry about smoothing it out. Try and build out the buttercream so it matches the depth of the board the cake is sitting on. Put it back in the freezer to firm up again. Use your putty knife to make the top level. Put the other 4.25? square on top. Begin scraping down the sides to match up with edges of the square top and bottom. Continue the process of applying buttercream, chilling and scraping off excess until you have nice straight sides and sharp corners. Use a ruler to help guide you in making the sides straight by putting the ruler flat on its end and seeing where there are gaps. Pull the cardboard square off the top before covering in chocolate.

Take a portion of your blue modeling chocolate and roll it out to 1/8? Use your ruler to check that the piece you roll out is roughly the size of one of the sides of your TARDIS. Use your x-acto to trim off the edges as close to the corners of your cake as possible. Use your ruler if you need to, to make straight cuts. Apply to all sides and top of the cake.

**update** I have learned since I made this tutorial that if you chill the panels of modeling chocolate in the fridge for a few minutes, they are easier to handle and cut. You can also chill panels of fondant if that is what you are using.

Roll out a second piece of thin modeling chocolate and apply over the first layer of modeling chocolate. At this point the cake should be sweating slightly so the chocolate should stick pretty easily. Trim off excess as we did in the first step. Use the ruler to measure out spaces for four windows. Don’t forget to leave space around the top and bottom edges to apply thin strips of chocolate as seen in the example photo. Use the x-acto blad to gently pull out the squares that will be the windows. Fix any seams with your ceramic tool.

Cut out some thin strips of chocolate about .25?. Apply these to the corners of the TARDIS. Use your ceramic tool to smooth out the edges and corners. Use the piece of cardboard that you pulled off the buttercream as a template to make a square piece of chocolate for the top of the TARDIS.

There is a slightly peaked piece of chocolate at the top of the TARDIS. To make this, start out with big piece of chocolate and use the rolling pin to create peaks. Start in the middle of the chocolate and roll towards one edge. Not too much pressure at first, more pressure towards the edge. You are trying to create a pyramid shape. Continue this process on all four corners starting from the center. Trim off the excess and place on top. Smooth down the rough edges and trim again if necessary.

Time to put in the light! Cute a hole through the thick piece of fondant that is as wide and deep as your floral light so that you can place the light into the hole and only the bulb shoes at the top. Fill the hole in with extra chocolate until the top is flush again.

Roll out a thin piece of chocolate into a square, use the cardboard template from before. Cut the square into four triangles. Cut the tips off the top of each triangle and place on top of the roof and smooth down the edges with your ceramic smoothing tool.

Use some small pieces of chocolate to make a snake. Cute into 4 pieces as tall as the light.  Roll out a small piece and use a round cutter to put on top of the light. Roll out small ball and squish it on top of the flat round piece and then a very small ball on top of that as seen in photo.

Cut out the police box signs and stick to some cut pieces of chocolate cut to size and apply to the tops of the TARDIS. Cut out the rest of the decals an apply according to photo

Paint the top set of windows with some black food color. Trim out some long thin pieces of white fondant. The windows should be the width of the ruler so use the ruler to judge how long the pieces should be. You can also pipe royal into the windows if you want but I preferred doing it this way although it is time consuming.

Use a flat brush to clean up any condensation or rough edges. Use your smoothing tool to clean up the edges and flatten any bumps on the surface. I spent way too long on this part but I’m obsessive. Finish the cake off by putting the TARDIS on your prepared board!

Check out the video below the finished project. I hope you enjoyed the tutorial!