To make the cake: Preheat the oven to 325 degrees F. Grease and line a quarter baking sheet with parchment paper. Set aside.
To a medium bowl, add the cake flour, baking powder and salt. Whisk until combined. Set aside.
In the bowl of a stand-up mixer, using the paddle attachment, beat the butter and sugar together until light and fluffy. Add the egg yolks and beat until completely combined, about 2 minutes. Next, add the vanilla extract.
Add the flour and milk, alternating between the two, starting and ending with the flour. Mix for about 20 seconds, until you no longer see any little speckles of flour. Pour the batter into the prepared quarter baking sheet and smooth out the top.
Transfer to the oven to bake for 17 to 20 minutes, until a cake skewer inserted into the center comes out clean. Allow to cool completely.
To make the frosting: In the bowl of a stand-up mixer, with the paddle attachment, add the butter, sugar, malted milk powder, melted (but cooled!) chocolate, vanilla and milk. Beat until smooth and fluffy, about 1 to 2 minutes. Set aside.
To arrange and decorate: Using a 3-inch cookie or biscuit cutter, stamp out cake rounds. You should get about 12. Transfer to the freezer to chill for 10 minutes.
Decorate the cakes as you like. I made one 4-layer cake, two 3-layer cakes and one 2-layer cake. I added sprinkles to the sides, to the tops and piped on little flowers and dollops. Get creative!