1. Place mint and ¼ cup sugar in a mortar/pestle and meddle well.
2. Stir mixture into boiling water, cover, and let stand for 5 to 10 minutes.
3. Spread the remaining sugar in a large, heavy skillet and cook over medium heat, stirring constantly until it is a dark amber color.
4. Add the diced mango and cook, stirring, until the caramel softens and dissolves.
5. Strain the liquid from the mint into the skillet, add the Plugrá Butter and cook 2 to 3 minutes more, mashing any remaining mango pieces.
6. Strain into a sauce bowl before serving. Serve warm.