In a saucepan cover the eggs with cold water, bring the water just to a boil, and simmer the eggs for 5 minutes. Pour out the water, add cold water to the pan, and let the eggs cool until they can be handled. Shell eggs carefully and halve them lengthwise. In a small bowl stir together garlic, mustard, vinegar, and cream. Add oils in a slow stream, whisking until emulsified, and season with pepper and salt. Cut pepper into 1/4-inch dice. Prepare grill. Halve each quail lengthwise through breast and pat dry. Rub quail lightly all over with oil and season with pepper and salt. Grill quail in a hot well-seasoned ridged grill pan over moderately high heat , or until skin is well browned but meat is still pink. In a large bowl toss watercress and mushrooms with just enough vinaigrette to coat lightly. Arrange lettuce on each of 4 large plates and top with watercress mixture and bell pepper and quail eggs. Arrange quail on top of salad and sprinkle with tarragon. Serve remaining vinaigrette on the side.
Recipe courtesy of Gourmet Magazine