Mennonite Red Cabbage and Apple Salad (Rotkohl und Apfelsalat)

4 cups shredded red cabbage
1 cup apples, quartered and sliced thin
1 teaspoon salt
2 tablespoons brown sugar
2 tablespoons vinegar
3 tablespoons butter
1/2 teaspoon mustard
1/2 cup sour cream
Pepper

Melt the butter in a saucepan. Add the cabbage and apple and stir until the butter coats the mixture and there are signs of softening, but the mixture is not really cooked. Add the vinegar, sugar, seasonings and mustard; simmer another 2 minutes, then stir in the sour cream. Serve hot.