In a small bowl combine mascarpone cheese, yogurt, vanilla and lemon zest. Cover and refrigerate.
Heat grill to medium high and oil grates with a bit of butter. Slice the peaches in half and remove the pits. Brush the cut side of the peaches with melted butter. Grill for about 3 minutes cut-side down, until there are some nice grill marks on the bottom of the peaches. Remove from the grill and let cool.
Put the Amaretti in a ziplock bag and roll with a rolling pin to crumble. Cut the peaches into bite-size pieces. Assemble 8 parfaits by layering the ingredients in individual 8-ounce mason jars as follows: Put peach pieces from 1/2 peach in the bottom of each mason jar. Follow with a tablespoon of the mascarpone and yogurt mixture and a teaspoonful of the Amaretti crumble. Repeat with a second layer. Cover the jars with lids and refrigerate until ready to serve. Remove lids before serving and garnish with a sprig of mint.