Cook rice in 1 cup water according to package directions to yield 2 cups cooked rice.
Preheat oven to 37
Place bread in a food processor; pulse 10 times or until coarse crumbs measure 1/4 cup.
Melt butter in a large nonstick skillet over medium heat.
Add leek; saut 6 minutes.
Sprinkle with flour; stir well.
Add milk; increase heat to medium-high, and cook, stirring constantly, until mixture comes to a simmer. Reduce heat; simmer 1 minute, stirring constantly.
Remove from heat; add rice, 1/2 cup cheese, and next 5 ingredients. Stir. Spoon into a 9-inch pie plate coated with cooking spray.
Combine remaining cheese and breadcrumbs; sprinkle over gratin.
Bake at 375 for 30 minutes or until set. Cool in dish 5 minutes on a wire rack.