**Prepare the Butter**

Start by beating the softened butter in a large mixing bowl using an electric mixer on medium speed. Beat until it becomes light and fluffy, about 3-4 minutes. This creates a smooth, creamy base for the frosting.

**Add Cocoa Powder**

Gradually sift the unsweetened cocoa powder into the butter, beating on low speed until fully incorporated. This helps avoid clumps of cocoa powder in your frosting.

**Add Powdered Sugar**

Add the powdered sugar, one cup at a time, and beat on low speed to combine. Once the sugar is incorporated, increase the mixer speed to medium and continue to beat until the mixture becomes smooth.

**Add Milk and Vanilla**

Slowly add the milk or heavy cream, one tablespoon at a time, until you reach your desired frosting consistency. Add the vanilla extract and a pinch of salt. Continue to beat until the frosting is smooth and fluffy.

**Adjust Consistency**

If the frosting is too thick, add a bit more milk (one tablespoon at a time) until it reaches the desired spreadable consistency. If it’s too thin, add a little more powdered sugar until it thickens up.

**Use or Store**

Once the frosting is smooth and fluffy, it’s ready to use! You can frost cakes, cupcakes, or cookies with it, or store it in an airtight container in the refrigerator for up to a week. Let the frosting come to room temperature and give it a quick stir before using.