Mix all ingredients in a saucepan, bring to a boil over medium heat, stirring occasionally. Simmer on low heat for about 5 min.
Cool. Then crush the mixture.
Prepare in sorbet maker according to directions. Place in freezer.
Soften a little before serving.
Serving suggestion: with a little bit of rhubarb compote (rhubarb very finely chopped, cooked for 2 min with very little water, sweetened as you like).