Combine the lemonade, thyme, lavender and sugar in a heavy small pan. Bring to a light simmer, stirring to dissolve the sugar. Allow to simmer for 2-3 minutes. Turn off heat, allow to cool for 5 minutes, cover and refrigerate until chilled or overnight.
Strain mixture (discarding the thyme and lavender), stir in the Citronage if using and process in an ice cream maker until frozen. Place in a sealed container in the freezer until fully set or overnight. Garnish if desired and serve!
Note: if you do not own an ice cream maker, you can freeze the sorbet according to the non-machine method used for Plum Rosemary Gin Sorbet.