Fresh Fruit, not bruised, as they come into season
Rum (60 proof); white rum is better as it imparts no colour
4 to 5 liter Clay or porcelain (not glass) crock
Wash and drain well 500g (1 pound) of fresh fruit. Add 250ml (1 cup) sugar, mix gently, let stand 1 hour before placing into crock
Pour on enough rum to cover the fruit by 1/2". The fruit will make juice, but at least half of the liquid should be rum. Keep the fruit submerged by inverting a small plate over the fruit and weight it down. The fruit must be completely covered with liquid.
Cover the crock with plastic wrap, and then put the lid on the crock.
Allow the mixture to stand at room temperature
Every two weeks add another in-season fruit. (Do not stir. Stir gently once or twice over the next two weeks)
The mixture will take at least two to three months to mature after you have added the last fruit. Stir before using. After the addition of fresh fruit it takes AT LEAST 2 weeks before fermentation is well under way again. The longer you allow the mixture to stand and ferment, the richer the Rumtopf. THAT is why the Rumtopf is traditionally begun in May or June and eaten during the Christmas season;6 months of richness!.
Blueberries and apples are the only fruits which do not do well in Rumtopf
Strawberries: wash, remove stems, whole or halve large fruits
raspberries/blackberries: do not wash, sort carefully, whole