Zwetschgenmus or Spiced Plum Butter
The plums are baked in a heavy cast iron pot until they turn into a sticky mass and are completely broken down. Make sure you use a four-quart cast iron pot. I used a smaller one in my first batch, and it took twice as long to bake them the next day. The second time, I used a four-quart pot and baked it in 2.5 hours instead of 4. Luisa Weiss says that the recipe is easily doubled, but unfortunately I ran out of plums.
5 one-pint size jars with lids and bands
4 pounds purple pitted plums (around 5 pounds with pits)
2 cups (200 g) granulated white sugar
1 cinnamon stick
2 whole clove
Wash, pit and quarter the plums. Discard those with dark spots inside. Put the plums, the sugar and the spices in a large bowl. Stir and cover the bowl with plastic wrap. Luisa puts her fruit in the same pot she uses for baking. Let the pot or bowl stand covered overnight until the sugar is dissolved in the juice of the fruit.
Heat the oven to 350ºF/180 Celsius. Pour the fruit into the pot, making sure you scrape every little bit of juice and sugar into the pot. Bake uncovered for 2 ½ hours, stirring occasionally. In the meantime, sterilize 5 one-pint containers. I run my jars and rings through the dishwasher and put my lids in a pot with hot water. Do not boil the lids
When the plums have broken down and the liquid in the pot has become syrupy, the Pflaumenmus is ready. Remove the pot from the oven. I put mine in the kitchen sink to prevent splattering. Remove the cinnamon stick, and if you see the allspice, remove that also (I didn’t see mine). Pureé the Zwetschgenmus with an immersion blender until smooth. I leave a few chunks of fruit in it. Fill the still warm jars with the plum butter. I have a wide funnel that really helps. Screw on the lid and turn the jar upside down. You will know your jars are sealed when the lid doesn’t move or pop when you press on it. To be totally safe, follow the manufacturer’s instructions that come with the jars.
recipe from Luisa Weiss in her Classic German Baking Book