- In a small bowl, combine the mint, jalapeño, lime juice, vinegar, and salt. Slowly add the oils in a thin, steady stream, mixing with a whisk or a fork until emulsified. Let sit for at least 5 minutes before using, so the mint and jalapeño flavors can marry and infuse the vinaigrette.
- Place the watermelon and tomatillos in a large salad bowl. Toss gently with enough vinaigrette to lightly coat. Sprinkle the cheese on top, garnish with mint, and serve.
Note: Vinaigrette can be made up to 3 days ahead, covered and refrigerated (mix well before using). Salad can be assembled without the cheese and mint garnish up to 12 hours in advance, covered and refrigerated.