For the cupcakes:

1. Preheat the oven to 350 degrees.
2. In a stand mixer using a paddle attachment, cream the butter and sugar until light and fluffy, about 3-4 minutes.
3. Add the eggs and vanilla and continue to beat for another 1-2 minutes.
4. In a medium size bowl, whisk the flour, cornstarch and baking powder.
5. Slowly add the dry ingredients to the wet ingredients until just combined. Pour in the milk and mix in.
6. Remove the bowl and by hand gently stir in the sprinkles, making sure not to over mix.
7. Fill lined cupcake pans until about 3/4 full and bake for 20-22 minutes or until toothpick comes out clean.
8. Remove from oven and cool completely.

For frosting:

1. Sift the powdered sugar in order to remove any lumps.
2. In a stand mixer using a whisk attachment combine the butter and sugar and beat on high until completely smooth and creamy. Add the vanilla extract and beat for an additional few minutes until fully combined.
3. Once cupcakes have cooled, spread the icing on and garnish with sprinkles.