To prepare Tamari-Ginger Dipping Sauce, combine all ingredients in a food processor or blender and process until the onion is finely chopped. Then set aside. Makes 2/3 cup.
To make Basic Batter: Mix flour, salt and pepper in a medium size bowl. Add eggs and milk, whisking gently until a smooth thick batter forms.
To make the Coconut Crust: Stir macadamia nuts, almonds and ginger into the batter. In a shallow bowl, combine the sesame seeds and coconut.
In a large heavy skillet, pour the oil to a depth of 3/4 inch and heat to 375°F
Peel Vidalia onion and cut crosswise into 1/2-inch thick slices; separate the slices into individual rings. (Reserve the onion centers for another use.) Dip an onion ring into the batter, coating thickly, then dredge in the sesame/coconut mixture. Lay the onion ring gently in the hot oil and cook until underside is dark golden, about 2 minutes; turn and cook 2 to 3 minutes longer. Remove and drain on paper towels. Keep warm in a 200 F oven.
Repeat with remaining rings. Cook 2 to 3 rings at a time depending on the size of your skillet, taking care not to crowd the pan or let the temperature drop too much, which will result in greasy rings. Serve warm with Tamari-Ginger Dipping Sauce.