In a cocktail shaker, muddle 2 thin slices of peeled fresh ginger with 1 teaspoon of sugar. Add 3 tablespoons of tequila, 3 tablespoons of mango nectar, 1 tablespoon of fresh lime juice, 1/2 tablespoon of triple sec and ice. Shake well and strain into a chilled martini glass. Garnish with a mango slice and serve.
To slice a mango for the garnish, peel it first with a sharp vegetable peeler or paring knife. Then, cut the flesh off the pit in 2 large pieces and slice them thinly.