Line baking sheet with parchment. Place three-fourths of white chocolate in microwavable bowl and melt on medium power (50%) for four 1-minute intervals, stirring after each. Add remaining white chocolate and let stand 5 minutes; stir until smooth. Spoon white chocolate onto prepared baking sheet, spreading into 8-by-12-inch rectangle. Let stand at room temperature until set, about 30 minutes. Repeat microwave melting process with semisweet chocolate; stir in EVOO. Spoon and spread on top of white chocolate. Sprinkle with candy corn and let stand until chocolate sets, at least 1 hour. Break into pieces.