1. Cake: Coat two 9 x 2-inch round baking pans with nonstick cooking spray. Line bottoms with waxed paper; spray paper.

2. Break up chocolate into a small microwave-safe bowl; add oil. Microwave on HIGH power for 1 minute; stir until smooth. If needed, heat an additional
15 seconds. Cool slightly.

3. In medium-size bowl, mix flour, cocoa, baking soda and salt. In large bowl, with mixer on medium speed, beat butter and sugar until fluffy, about 3 minutes. Add eggs, one at a time, beating after each. Beat in chocolate mixture and vanilla.

4. Place vinegar in a 2-cup capacity measuring cup. Add milk and stir until blended. On low speed, beat flour mixture into butter mixture, alternating with milk, beginning and ending with flour; beat 1 minute. Spread into pans.

5. Bake at 350 degree F for 35 minutes or until toothpick inserted in centers tests clean. Cool cakes in pans on wire racks 15 minutes. Turn cakes out onto racks; cool layers completely (about 2 hours).

6. Prepare Frosting: In large glass bowl, microwave white chocolate on 50% power for 1 minute; stir. Microwave another 30 seconds until melted and smooth. Let cool slightly.