Heat oil in a large skillet over medium-high. Sprinkle chicken with 1 teaspoon salt and 1/2 teaspoon pepper. Add chicken to pan; cook 3 minutes on each side. Divide chicken between 2 square (8-inch) baking dishes coated with cooking spray. Bake at 350°F for 10 minutes or until done. Cool and chop.
Return skillet to medium-high. Combine flour and 1/2 cup milk in a bowl. Add leeks and next 4 ingredients (through mushrooms) to pan; cook 13 minutes or until browned and tender. Stir in flour mixture, remaining 4 1/2 cups milk, and parsley; cook 3 minutes. Stir in cream cheese until smooth; cook 2 minutes or until slightly thickened. Combine chicken, remaining 1 teaspoon salt, remaining 1/2 teaspoon pepper, mushroom mixture, rice, and green onions in a bowl. Coat baking dishes with cooking spray. Divide chicken mixture between dishes; top with almonds. Follow freezing directions, or bake at 350 degrees F for 30 minutes or until browned and bubbly.How-ToFREEZE: Cool mixture completely. Cover with heavy-duty foil or airtight lids. Freeze up to 2 months.THAW: Uncover and microwave at MEDIUM (50% power) 15 minutes or until thawed.REHEAT: Cover and bake at 450 degrees F for 25 to 30 minutes or until thoroughly heated.