Combine all ingredients in a preserving pan. Heat the mixture slowly over medium heat, stirring it gently now and then with a rubber spatula, until it begins to boil. Lower heat and simmer the mixture, stirring it occasionally as gently as possible, until fruit is tender and syrup has thickened slightly, about 30 minutes. Taste; add more sugar if needed. Remove cinnamon pieces.

Ladle boiling-hot sauce into hot, clean half-pint canning jars, leaving 1/4" of headspace. Seal jars with new two-piece canning lids according to manufacturer's directions; process for 15 minutes in a boiling-water bath. Cool, label, and store the jars. Alternatively, store the sauce, unsealed, in the refrigerator for use within 2 months or so. Canned, this keep in a cool pantry for up to a year.

Witty writes: "This sauce revives a two-fruit combination (counting rhubarb as a fruit) that was a favorite pie filling back when a day without pie was a day without proper provender. Orange and a touch of cinnamon have been added here. The blueberries dye the rhubarb their own deep purple-red and share their flavor with it, too. The sauce can be made satisfactorily from frozen blueberries and rhubarb, two raw materials that withstand freezing very well. Not incidentally, the presence of the rhubarb is essential (for texture) and almost unguessable."

Some serving suggestions:

~ Ladle sauce, which should be at room temperature, over vanilla, peach, or lemon ice cream; bring out the butter cookies or vanilla wafers.

~ Spoon sauce over slices of sponge, butter, or angel cake; top the dessert with a tuft of whipped cream. (Our grandmothers would have baked a cottage pudding - an eggless plain cake served warm - for a dessert like this.)

~ For a pudding-parfait, make alternate layers of vanilla-flavored soft custard and blueberry-rhubarb sauce, ending with a spoonful of the sauce. Or use ricotta, whipped lightly, in place of the custard.

~ For optional oomph, spike the sauce with a little brandy, preferably Armagnac.

From "Fancy Pantry" by Helen Witty. New York: Workman Publishing Company, Inc., 1986. Pp. 248-249. Isbn 0-89480-037-X. Posted by Cathy Harned. From: Cathy Harned