Prepare the pastry shells according to package directions; set aside. Place the cauliflower in steamer basket. Place in a saucepan over 1 in. of water; bring to a boil. Cover and steam for 5-8 minutes or until cauliflower is crisp-tender.
In a skillet, saute onion and mushrooms in butter until tender. Stir in the flour, bouillon and pepper until blended. Gradually add milk. Bring to a boil; cook and stir for 2 minutes or until thickened. Stir in ham and cauliflower. Remove from the heat. Stir in cheese until melted. Spoon into pastry shells.