In a large bowl, combine the potatoes, butter, salt and pepper. Press into 6 10 oz custard cups sprayed with non stick spray; set aside
In a large saucepan, saute onion in butter. Add the flour, bouillon, Worcestershire sauce and basil. Stir in milk. Bring to a boil; cook and stir for 2 minutes or until thickened. add chicken and mixed veggies. Spoon into prepared crusts.
Bake, uncovered at 375 for 30-35 minutes or until crust is golden brown.