Combine boiling water and Splenda Stevia Sweetener in a large bowl, stirring until sweetener dissolves. Cool slightly.
Stir in lemon juice and zest.
Pour mixture into a 9” square pan; cover and freeze until firm, about 2 hours.
To serve, cut tops from lemons; remove pulp. Set aside.
Remove sorbet from freezer; let stand about 10 minutes. Scrape sorbet surface with a spoon. Scoop sorbet into lemon shells or into small serving dishes. Garnish with fresh mint, if desired