Place the first 8 ingredients in a medium pot and whisk until smooth. Bring to a simmer and cook 1 minute. (The mixture will be thick, but will loosen once the rhubarb cooks.)
Add the rhubarb to the pot and return to a simmer. Gently simmer rhubarb until just tender, but still holding its shape, about 5 minutes. Remove from the heat, cool to room temperature, and then mix in the mint. Spoon compote into a tight sealing jar and refrigerate until needed. Will keep about a week.
Note: Three medium stalks of rhubarb should yield the diced amount called for in this recipe. To dice the rhubarb, first cut the stalks in half lengthwise. Now cut, widthwise, into ¼ to ½ inch thick pieces.