Turn the oven to 375°F so it can heat up while you prepare the dough.
In a large mixing bowl or stand mixer, cream together the butter and sugar.
Mix in the egg and vanilla.
Add the baking soda, baking powder, salt, and flour and mix it all together.
On a piece of parchment paper, roll out the dough into a big circle until it's about 1/4 inch thick and around 12 inches across. Move the parchment paper with the dough on it to a baking sheet.
Bake in the preheated oven for 12-15 minutes, or until the edges are starting to turn a golden brown. Allow to cool compeltely.
To make the frosting, beat together all of the frosting ingredients until smooth.
Once the cookie base is completely cool, spread the frosting all over it.
Top with any fruits you'd like.