1. Heat rice according to package directions.
2. Stir together rice, next 3 ingredients, and, if desired, chicken. Spread 1/2 cup rice mixture just below center of each tortilla. Fold bottom third up and over filling of each tortilla, just until covered. Fold left and right sides of tortillas over, and roll up. Place, seam sides down, on a lightly greased jelly-roll pan. Brush tops of tortillas with melted butter.
3. Bake at 400° for 15 to 18 minutes or until golden brown. Serve with desired toppings.
*1 (15-oz.) can black beans, rinsed and drained, may be substituted.
Note: For testing purposes only, we used Rice-A-Roni Express Mexican. To make ahead, prepare chimichangas as directed through Step 2; cover and chill 8 hours. Let stand at room temperature 30 minutes; bake as directed.