In a mixer with the paddle attachment, beat together the butter and shortening until blended.
Add vanilla and beat until blended
Add powdered sugar, 1 cup at a time and scraping the sides of the bowl as needed until all ingredients are incorporated.
Add milk, 1 Tbsp at a time until frosting is the right consistency.
Beat frosting on high for 2 minutes until light and fluffy.
Add crushed Oreos and beat for another 30 seconds
Add a little more milk if the frosting seems to stiff.
Frost the cupcakes with the icing (or you can use a basic piping bag and tip). Stick a mini Oreo in the icing for decoration