Preheat oven to 350º F. Prepare rice according to package directions. In a small bowl, beat egg yolks and combine with 1/4 cup milk and corn starch. In a medium sauce pan combine cooked rice, remaining milk, brown sugar and butter. Bring to a boil. Reduce heat to medium and stir in egg mixture. Cook over medium heat, stirring constantly until thickened. Remove from heat and stir in vanilla. Pour into individual ovenproof serving dishes. In a small bowl, combine sugar and coffee powder. In a large bowl, beat egg whites until frothy. Add sugar mixture gradually and beat until egg whites are stiff but not dry. Spread meringue over pudding. Bake for 10 minutes or until golden brown. Serve warm or cold.