Preheat oven to 325 degrees F. If macadamia nuts are salted, blanch in boiling water to cover for 30 seconds to remove salt. Rinse under cold running water and transfer to a baking sheet. Toast in a 325 degrees F oven until golden brown. Let cool, then coarsely chop. If nuts are unsalted, just toast and chop.

2. Combine flour, baking powder, and salt. Set aside.

3. Place butter, sugar, and water in a medium saucepan over low heat. Cut 6 ounces of the white chocolate into large (1- or 2-inch) chunks and the remaining 3 ounces into small (1/4-inch to 1/2-inch) chips.

4. When butter has melted, remove from heat, add the 6 ounces white chocolate chunks and stir until chocolate melts.

5. Beat in eggs and vanilla. Stir in flour mixture until just blended. Stir in the 3 ounces of white chocolate chips and the nuts.

6. Spread batter in a greased 8- or 9-inch square baking pan. Bake 30 to 35 minutes, or until a toothpick inserted in center comes out clean. Cool on a wire rack, then cut into squares.

* Timesaver Tip: Brownie batter can be made ahead and frozen before baking. Line an 8- or 9-inch square pan with heavy-duty foil. Spoon batter into pan. Freeze batter, uncovered, until frozen solid. Remove from pan and wrap tightly. Label and date package. Freeze at 0 degrees F up to 4 weeks. To bake, peel foil from batter and place in greased pan. Bake in a preheated 375 degrees F oven until skewer inserted in center comes out clean (40 to 50 minutes).

Microwave Version: Chocolate may be melted in a microwave oven. Place butter and chocolate in a small glass bowl. Microwave on 50% power for 1 minute, stir, then continue microwaving 1 to 3 minutes more. Stir until smooth. Do not overheat or chocolate will scorch around edges and won't blend smoothly. Stir in sugar and water and continue with step 5.