1. Line a large cookie sheet with waxed paper. Pour white chocolate into a 9-inch glass pie plate. Pour semisweet chocolate into a bowl.
2. Dip a spoon into the semisweet chocolate, then drizzle parallel lines of about 3/4 inch apart onto white chocolate in pie plate. Set aside remaining semisweet chocolate.
3. Make sure strawberries are completely dry. Holding one strawberry by its hull, dip strawberry into both chocolates, pressing opposite sides of strawberry across dark and white lines to form 2 marbleized flower petals. Lift strawberry and jiggle gently to drain off excess chocolate. Place strawberry on prepared cookie sheet. Repeat process with remaining strawberries and chocolates and arrange 1-inch apart on prepared cookie sheet. Periodically drizzle more lines of semisweet chocolate across white chocolate. (If white chocolate starts to harden, microwave on Medium for 30 seconds or just until softened; do not stir.)
4. Refrigerate strawberries until chocolate is firm, about 5 minutes. Makes about 28 strawberries.