Crab and Shrimp Enchiladas

1/4 cup butter
1/4 cup flour
2 cups chicken broth
2 cups (8 ounces) Monterey Jack cheese, shredded
3/4 cup half-and-half
1/4 teaspoon salt
1/8 teaspoon pepper
1/2 cup sour cream
2 - 8 ounce packages imitation crab
8 ounces cooked small shrimp (salad shrimp)
1/2 cup sliced green onions
8 - 8 inch flour tortillas

Heat oven to 350 degrees. Spray a 13x9x2 glass dish with nonstick cooking spray. Melt butter in saucepan. Whisk in flour. Slowly whisk in broth. Bring to a gentle boil. Whisk in cheese, half-and-half, salt and pepper. Place sour cream in bowl; slowly whisk in 1 cup of sauce. Whisk sour cream mixture into remaining sauce. Remove from heat. In bowl combine crab, shrimp, 1 cup sauce, and 1/4 cup green onions. Place 1/2 cup crab and shrimp filling on each tortilla. Roll up; place in dish. Cover with remaining sace. Bake 20-25 minutes or until hot. Let stand 5 minutes; sprinkle with remaining 1/4 cup green onions.