Start with room-temperature butter. It should be soft but not melted (see note 2).
No need to separate the cookie from its filling—just toss whole Oreo cookies into a powerful blender or food processor and pulse until you have 1 cup of fine crumbs.
Add room-temperature butter to a stand mixer with the paddle attachment (or in a large bowl if using a hand mixer.) Mix at low speed until creamy. Avoid whipping.
Gradually add powdered sugar, about 1/2 cup at a time, pausing the mixer each time to prevent a cloud of sugar. Keep the mixer at low speed until the sugar is fully combined with the butter. Scrape the sides and bottom of the bowl to ensure all ingredients are incorporated.
Add Oreo crumbs, vanilla extract, and salt. Keep the mixer on low speed and gradually add heavy cream (starting with 2 tablespoons). Mix until the cream is combined with the other ingredients.
If the frosting is too thick, add an additional teaspoon of heavy cream, one at a time. Continue until you achieve the desired thickness for your frosting. Taste the frosting and add more salt if desired, to intensify flavors or further balance the sweetness.
Once ready, spread or pipe the frosting onto completely cooled cupcakes or cake.
Notes
Note 1: This recipe makes enough to frost a 9x13-inch cake, a 2-layer cake (8 or 9-inch rounds), 24 cupcakes, or generously frost 12 cupcakes as shown in the post photos.Note 2: Butter should be soft but not melted—cool to the touch, holding its shape, yet slightly pliable. Too soft, and the frosting may be loose; too cold, and it could get lumpy. (Check the post for quick softening tips!)Note 3: Ensure the measuring cups are fully filled with powdered sugar, and use the back of a table knife to level off the top when measuring for this recipe.Nutrition Note: Nutrition information is for one serving, based on 12 servings per batch of frosting.Storage: Keep leftover frosting in an airtight container in the fridge for up to 1 week or freeze for 3 months.