Grease and flour a 12-cup bundt pan. Set aside. DO NOT preheat the oven.
In a large bowl, use a mixer to cream shortening, butter, cream cheese, and peanut butter until smooth. Gradually add the sugar, beating until light and fluffy. Add eggs one at a time, beating well after each.
In a small bowl, whisk together the flour, baking powder, and salt. Gradually add the flour mixture to the creamed mixture, blending well. Add the vanilla and mix well.
Pour into the prepared pan. Place in a cold oven. Bake at 325°F for 1 hour and 15 minutes or until toothpick inserted in the center of the cake comes out clean. Allow to rest in the pan for about 10 minutes, then invert onto a serving platter.
Make the glaze icing by mixing the sweetened condensed milk, peanut butter, and milk together until smooth. Pour over cooled cake.