Preheat the oven to 160C/Gas Mark 3.
Prepare your Giant Cupcake Tin or silicone mould – use a liberal amount of vegetable oil, and get into all the creases and grooves.
Put all the ingredients except for the milk in the processor and then blitz till smooth. Pulse while adding milk, to make for a soft, dropping consistency, down the funnel. Alternatively put all ingredients into a large mixing bowl and use an electric hand mixer. Or using a bowl and wooden spoon, cream the butter and sugar, beat in the eggs one at a time with a little of the flour. Add the vanilla extract and fold in the rest of the flour, adding the milk to get the dropping consistency as before.
Fill the 2 parts of the giant cupcake tin to just about 2cm short of the rim of the tin.
Bake in the oven for 55 - 65 minutes, checking that the centre of the base (slightly larger than the top piece) is cooked through fully by inserting a skewer.
Remove from the oven and allow to cool for 25 minutes in the tin. It’s important to let the cake firm up before you attempt to get it out of the tin. Don’t let it cool fully in the tin otherwise it will start to sweat and will be harder to release.
To turn them out place a cooling rack on the top of the tin and flip them over together. Give it a sharp shake to release the cakes and then gently lift the tin away.
If they haven’t both released a sharp tap should do the trick and the cakes will come away cleanly. Allow the cakes to cool fully on the wire rack before trimming off any domed excess to give both the base and the lid a flat surface to buttercream together.
For the buttercream, mix the butter with the icing sugar and vanilla essence and a few drops of food colouring. Continue to mix until smooth adding the milk to loosen the buttercream.
Take some of the buttercream on a palette knife and spread thickly on the top of the base of the giant cupcake. This layer should be approximately ½ cm thick. Spread the buttercream using a palette knife on top of the giant cupcake to the thickness you desire, smoothing gently with the palette knife.
To create the rose effect use a 1M, or 2D nozzle tip in a medium piping bag (or any large open star tip) 2/3 fill with buttercream and seal bag. To create the rose effect, Start piping at the centre of the rose pattern about 2” up from the bottom edge of the top cake. Slowly work your way around going anti-clockwise until you reach the outer edge of your giant cupcake. Remember to apply even pressure to your piping bag, this insures an even swirl all the way around. Pipe so the icing is touching the next rose to minimise gaps. Make a second row of roses, and finish off with a final one on top. Fill in any gaps between the roses with a small piped rosette.
For the flower decorations, take some mini marshmallows and cut in half diagonally across the middle. Take 3 sandwich bags and fill one ¼ full with yellow glimmer, one ¼ full with blue glimmer and the other ¼ full with pink glimmer sugar. Add the cut marshmallows to each bag and give a shake. The cut side is sticky and will stick to the coloured sugar.
Gently push them into the buttercream, creating a circle from approximately 10 marshmallows. Have the ‘pointy’ part of the cut marshmallow pointing outwards. Complete the circle. Now create a second inner circle of petals in the same way using 5 petals. Place a gold dragee in the centre of the flower. Carry on round the giant cupcake with these marshmallow flowers, filling any gaps with a small flower made from 5 petals.