In a saucepan, add fresh blackberries and lemon juice. Cook over medium heat, stirring frequently until the mixture reduces to about 1/3 cup, which typically takes around 20 minutes.

If you prefer a smoother frosting, strain the blackberry mixture with a fine mesh sieve to remove the seeds, creating a velvety texture.

Allow the blackberry puree to cool completely. This step is crucial to ensure the butter doesn’t melt when combined.

In a mixing bowl, beat the softened unsalted butter until smooth and creamy.

Gradually add the cooled blackberry puree to the butter, mixing until completely combined and you achieve a beautiful purple hue.

Slowly incorporate powdered sugar, beating on medium-high speed until the mixture is light and fluffy, usually about 2-3 minutes.

Add vanilla extract and milk or cream one tablespoon at a time until you reach the desired consistency for spreading or piping.

For an extra berry burst, consider folding in small pieces of blackberries at the end.