How to Make It
Remove the stem tips with a few leaves attached from 4 to 6 of the mint sprigs, and set them aside for use as a decoration. Gather the remaining sprigs of mint into a bundle, and tie them together with kitchen twine. Place the mint in a saucepan (preferably stainless steel), and add all the remaining ingredients except the berries, sour cream, and pound cake.
Bring the mixture to a boil, cover, reduce the heat to low, and cook for about 8 minutes. Add the berries, bring back to a boil, and cook, covered, for 2 minutes. The mixture should be somewhat soupy. Cool, cover, and refrigerate until serving time.
For each serving, arrange about 1 cup of the rhubarb and berry mixture in a deep plate. Place 1 rounded tablespoon of sour cream in the middle. Top with one of the reserved mint sprig tips. Serve with a slice of brioche or pound cake or a few cookies.