Beat together the butter and sugar until creamy and thoroughly mixed.
Add in the plain flour, and vanilla, and beat again until a dough is formed. It can be a little crumbly, but it does come together.
Get two larger pieces of parchment paper, and roll 1/3 of the dough in between it.
Roll out so it's larger than your largest bowl, and then lightly cut around the bowl, without cutting through the paper. Add a smaller bowl to the middle, and cut around that as well, and remove the excess dough.
If using the shape of a letter, or number, cut out around a stencil lightly, and remove excess dough.
Repeat the process again, for the other two layers.
Place the three large cookies in the fridge for at least 30 minutes, or the freezer for 10 minutes.
Preheat your oven to 180C/160C fan, and then bake the cookies in the oven for 12-15 minutes, or until they are lightly starting to brown. Leave the cookies to cool fully on the tray.
With the excess dough, you can cut out any shapes of cookie you want. They will take about 10 minutes to bake, at the same temperature.
For the Buttercream
Make sure your butter is at room temperature.
Beat the butter on it's own for a few minutes to loosen it and make it lighter.
Add in the icing sugar and beat fully to incoporate it!
Add in the vanilla, and keep on beating the buttercream for about 5 minutes to make it lovely and light and fluffy!
For the Decoration
Add a bit of buttercream onto your serving plate to stick the first biscuit down.
Carefully add on your first biscuit shape, and pipe on your buttercream! You can use whatever piping tip you like!
Add on the second biscuit and repeat!
Add on the third biscuit, and repeat again.
Now top with whatever you like - raspberries, chocolate dip strawberries, mini meringues, sprinkles, chocolate shards, blueberries, freeze-dried fruit and so on!
For this, it's best not to overthink it, and just go with the flow! I usually add on the larger objects, and then go down in size to make sure everything fits!
You can of course cut whatever biscuit shape you like! I just did the circles as the easiest example.
I don't add measurements for the decorations as this can vary on the size of the biscuit cake you make, or shape.
Also, some people may want to decorate it differently!
I would store this in the fridge personally, and it lasts a good 2-3 days!