Preheat oven to 350°F.
Spray a 9 inch springform pan with cooking spray and dust with 2 Tbsp sugar. In a large bowl, beat butter with mixer at medium speed until light and fluffy. Beat in vanilla, then egg whites (one at a time). Combine flour, baking soda, and salt in a small bowl. In another bowl combine milk and buttermilk. Add flour mixture and buttermilk mixture alternately to the sugar mixture. Fold in coconut.
Spoon cake mixture into prepared pan and bake in preheated oven for 55 minutes or until a wooden pick inserted in center comes out clean. Cool 15 minutes on a wire rack, then remove from pan and cool completely on wire rack. Sprinkle with powdered sugar.
For Ginger ice milk, combine water and ginger in small saucepan and bring to a boil and then drain. Combine ginger, milk, and sugar in medium saucepan. Scrape vanilla seeds from pod and add to saucepan. Heat saucepan over medium heat until tiny bubbles form around edge (do not bring to a boil). Remove from heat.
Place eggs in a large bowl. Gradually add hot mil mixture, stirring constantly with a whisk until blended. Let stand 15 minutes. Strain milk mixture through a sieve into a pan and discard solids.
Heat milk mixture over medium heat, stirring constantly until thermometer reaches 160°F Cool completely. Pour mixture into the freezer can of an ice-cream freezer, and freeze according to manufacturer's instructions.