Green (unripe) mango is not as sweet as it is when it ripens, so it has a much smaller glycemic impact and gives this salad a tangy taste. Madras curry powder is hotter and more nuanced than regular curry powder. The chili paste adds more heat.
Place the curry powder, basil, cilantro, 1 tablespoon of fish sauce and canola oil in a food processor and pulse to blend well. Pour into a bowl and add the shrimp. Marinate for 1 hour at room temperature.
In a medium bowl, toss together the mango, radishes, lime juice, 1 tablespoon of fish sauce, olive oil and chili paste (if using). Divide the salad into four portions and place each on a plate.
Preheat the grill to medium-high. Grill the shrimp for about 1 minute on each side.
To serve, place 4 shrimp on top of each portion of mango salad.