In a microwave or in a large saucepan over low heat, melt marshmallows and oil; stir until smooth. Stir in extract; remove from heat. Stir in cereal and 2/3 cup sprinkles. Press mixture into a lightly-greased 13x9-in. baking pan using wax paper or a lightly-greased spatula. Cool to room temperature. Spread melted white baking chips on top; sprinkle with remaining 1/3 cup sprinkles. Cut into bars.