In a large mixing bowl, add the room temperature unsalted butter. Using an electric mixer, beat the butter on medium speed until it is smooth and creamy, about 2-3 minutes.
Once the butter is creamy, add the pure vanilla extract. Mix for an additional minute until fully incorporated.
In a separate bowl, whisk together the powdered sugar and unsweetened cocoa powder to break up any lumps.
With the mixer on low speed, gradually add the dry mixture to the butter mixture. Start with about a cup at a time, mixing until just combined before adding more.
Once all the dry ingredients are combined, add the whole milk. Beat on medium speed until everything is well blended and the frosting is light and fluffy.
Give your frosting a taste! If you want it sweeter, you can add a little more powdered sugar. If you prefer a richer chocolate flavor, add a touch more cocoa powder.
Now, it’s time to spread or pipe your Chocolate Buttercream Frosting onto your favorite cakes or cupcakes. Get creative with your designs, and enjoy the delicious results!