1. Place the matcha into a heatproof jug or bowl. Pour the boiling water over the matcha and whisk to dissolve it.
2. Mix in the agave and lime juice. Cool this mixture to room temperature, and then cover and refrigerate until ready to serve.
3. To serve, fill four glasses with ice. Add 4 to 5 mint leaves to each glass. Whisk the matcha mixture until even, and then divide and pour into the glasses.
4. Garnish each glass with a lime slice and serve. Enjoy!