Put the pitted mirabelle plums in a large saucepan and cook over high heat. Stir regularly. The fruits release liquid quickly and soften quickly. Puree the fruits (we like a very fine, creamy jam without large pieces of fruit, but you can do that as you wish).
Add the preserving sugar and bring to the boil, stirring constantly. Let the jam simmer for about 3-4 minutes.
Finally add the Aperol. Stir briefly and immediately pour into the prepared glasses.
You get a fruity jam with a slightly bitter, special note from the Aperol.