In a large heat-safe bowl, place the mangos, tarragon and thyme sprigs, and black pepper; set aside.
In a small saucepan set over medium-high heat, bring to a simmer the rice vinegar, water, sugar and salt.
Pour the hot vinegar mixture over the mangos and cool to room temperature, about 30 minutes.
Cover the bowl with plastic wrap and refrigerate overnight (the mangos keep up to 1½ weeks in the refrigerator).
In a small bowl, whisk together 1/3 cup of the mango pickling liquid, the olive oil, and salt and pepper to taste.
Divide the salad greens and fennel among 4 plates.
Sprinkle each plate with 1/4 cup pickled mangos, then drizzle the vinaigrette over the salad.
Top with the crumbled cheese and serve.
Recipe from the Tasting Table Test Kitchen