Halve the papaya and remove the seeds. Peel the papaya and cut into cubes. Puree the papaya in a blender with the orange, lemon juice, honey, and lemon balm leaves.
Fill 2 highball glasses with ice cubes.
Mix the buttermilk and vanilla into the papaya puree, and stir until combined. Pour into the glasses, garnish with lemon balm leaves, and serve.