Method:
Preheat oven to 325°F. Use a vegetable peeler to remove outer peel from mandarins, and then finely chop it to obtain 1 tablespoon zest. Juice mandarins to obtain 1/4 cup juice. Set aside. In a large bowl, beat 1 1/4 cups sugar and oil on medium speed for 1 minute. Add juice, zest and vanilla and beat again. Add flour, 1/2 cup coconut, cornstarch, baking powder and salt; beat again until combined. In a bowl, combine remaining 1/2 cup sugar and 1/2 cup coconut.
Form dough into 1 1/2-inch balls. Arrange 2 inches apart on a parchment-paper-lined baking sheet. Dip a flat-bottomed glass in water and then in sugar mixture. Press down firmly on each cookie, re-dipping the glass as needed. Bake until golden brown and just firm, about 15 minutes.