Preheat oven to 350F (180C). Line standard muffin tins with paper liners.
With a mixer (or stand mixer) beat butter and sugar. Add egg and keep beating.
In another bowl mix flour, baking powder and salt.
Incorporate the flour mixture with the butter mixture. Pour the milk and beat until batter is smooth.
Pour batter in lined cups. Bake until a cake tester inserted in center comes out clean, about 20 minutes.
Frosting
Place butter and cream cheese into a bowl and whisk on high speed until it reaches a whipped cream texture. Add sugar and vanilla and whisk on high speed for about 30 seconds.
Assembling
Place frosting in a pipping bag. Using a small tip make a layer of frosting in circular movements (picture above). Then, on top of this, shape the frosting like it's a brain (picture above). First one half, then the other half.
Now take the strawberry jam. Add some water to make it less thick. Pour some jam on top of the "brain" and fill the serynges with jam. Stick one serynge in each cupcake.
Before eating, "inject" the jam from the serynge in the cupcake.