Wash and stone the mirabelle plums. Score the top and bottom of the vineyard peaches in a cross shape and place in boiling water for 1 minute, then peel and stone them.
Mix the mirabelle plums and lemon juice with the preserving sugar and let stand for about 3-4 hours, stirring occasionally. Add pieces of vineyard peaches. Puree with the hand blender or puree completely, depending on your taste. Boil everything together. Add 2 sprigs of rosemary (several for a stronger aroma). When it boils bubbly, let it simmer for at least 4-5 minutes. The foam formation is reduced again by the bubbly boiling. Remove the rosemary sprigs again.
Fill jam full to the brim in clean jars and turn them upside down.
Tip:
If you want, you can also cook some seeds, these will enhance the taste. I still had a couple of plums left and I just helped process them. They only optically create nice splashes of color in the glass. Makes about 4-5 glasses.