Cream butter, shortening and sugar till fluffy. Add eggs, one at a time. Add vanilla to milk. Combine flour with baking powder.
Add liquids and flour mixtures alternately to butter/egg mixture in several batches, ending with milk.
Pour batter into prepared pan. Place pan in cold oven and set to 300F. Bake for 2 hours.
Note: this is versatile. Try extracts other than vanilla, or add mini chocolate chips...and now that the dried berries are so easily found in most major U.S. cities, they're winners, too.