Traditional preparation
German Rote Grütze (″Hamburg style″ with vanilla sauce)

Rødgrød or Rote Grütze was traditionally made of groat or grit, as revealed by the second component of the name in Danish, German, or Low German.[1][2] Semolina and sago are still used in some family recipes; potato starch is today the standard choice to achieve a creamy to pudding-like starch gelatinization. The essential ingredients that justify the adjective are red summer berries such as redcurrant, blackcurrant, raspberries, strawberries, blackberries, bilberries and stoned black cherries. The essential flavour can be achieved with redcurrant alone; a small amount of blackcurrant will add variety; sugar is used to intensify the flavour. The amounts of starch, sago, semolina differ with the solidity desired; 20 to 60 grams on a kilogram or liter of the recipe are usual; sago, groat or grit have to soak before they can be used.

The preparation is basically that of a pudding: The fruits are cooked briefly with sugar. The mass should cool down for a moment so that the starch—dissolved in fruit juice or water—can be stirred into it without clumping. A second cooking process of one to two minutes is needed to start the gelatinization; remaining streaks of white starch have to clear up in this process.

Rødgrød or Rote Grütze is served hot or cold as a dessert with milk, a mixture of milk and vanilla sugar, vanilla sauce, (whipped) cream, vanilla ice cream, or custard to balance the refreshing taste of the fruit acids.
https://en.wikipedia.org/wiki/R%C3%B8dgr%C3%B8d