Step #1 In a saucepan mix the plums, the lemon juice, & 1/4 c water & cook the mixture over moderate heat, stirring every once in awhile, for 10 to 15 mins, or until the plums are soft.
Step #2 While the plums are cooking, cook the mixture over moderate heat, until the sugar is dissolved, in a small saucepan mix the sugar & 3/4 c water, stirring, stir in the the kirsch.
Step #3 In a mixer or food processor/blender puree the plums with the kirsch syrup.
Step #4 Strain the puree through a fine sieve into a bowl, let it cool, & freeze it in an ice-cream freezer according to the manufacturer's instructions.