Place the mint, basil, garlic, lemon juice, salt and pepper in a blender or a food processor and process to blend, scraping down the sides. Drizzle in the olive it until it becomes a loose paste, adding as much as needed to get to the texture and concentration you like. Pulse in the Parmesan.
Drizzle and dollop over tomatoes.
Notes
This makes a pretty thick pesto, and you can add some additional olive oil if you like.
Consider putting the tomatoes on some amazing grilled or toasted bread.