In the bowl of a food processor, process the Oreos to make very fine crumbs. (You can also put them in a zip-top plastic bag and crush them very finely with a rolling pin.)
In the bowl of a stand mixer fitted with a paddle attachment, beat the butter on medium speed for about 2 minutes until creamy.
Add the vanilla extract, salt, and half of the powdered sugar. Beat on low speed for 30 seconds, just until combined.
Add 1 tablespoon of heavy cream and the remaining powdered sugar. Beat on low speed for 30 seconds just until combined. Increase the speed to medium and beat for 2 minutes until light and fluffy.
Add the pulverized Oreos and beat on medium speed for 30 seconds to 1 minute until well combined. (If the buttercream looks dry and not creamy, add the remaining heavy cream, 1 teaspoon at a time and mix to combine.)
Notes
Use softened butter. Softened butter is a must for a velvety frosting. Butter that’s straight out of the refrigerator will not become fluffy. Set the butter out about an hour before you start baking. If you forget, follow my simple steps for how to soften butter quickly.
You can use whole milk or half and half in place of the heavy cream.
A note on heavy cream: I tend to only need 1 tablespoon of heavy cream when I make this frosting. But if the buttercream looks dry, add the remaining heavy cream, 1 teaspoon at a time, and mix to combine.
Topping ideas for cakes and cupcakes: I like to garnish with more crushed Oreo cookies or half of an Oreo cookie pressed into the icing. Mini Oreos also make a cute topping.