Bring milk to a slow boil in a saucepan; gradually add cornmeal, stirring constantly. Reduce heat to low and cook, stirring constantly, 10 minutes or until thickened. Remove from heat; add butter and baking powder and stir until butter is melted. Let cool and set aside.
In a small bowl, use a fork to beat egg yolks until light; stir into cooled cornmeal mixture. Add ham and mix until blended; set aside. Beat egg whites at medium speed with an electric mixer until stiff peaks form; fold into cornmeal mixture until well combined.
Pour into a greased 2-quart casserole dish; bake at 350° for about 40 minutes or until a toothpick inserted in center comes out clean.