Place oven rack in center position and heat oven to 350 degrees. Grease a 10-inch tube pan; dust with flour and tap out excess. Set aside. Spread chopped nuts evenly on a baking sheet and toast until fragrant, about 5 to10 minutes. Set aside to cool.
To make cake, lightly spoon flour into dry measuring cups, and level with a knife. In a medium bowl, sift together flour, baking powder and salt three times. In a large bowl using an electric mixer, beat butter and shortening at medium speed until light and fluffy. Gradually add brown sugar, granular sugar and vanilla, beating until well-blended. Add eggs, 1 at a time, beating well after each addition. Add flour mixture to sugar mixture alternately with milk, beating at low speed, beginning and ending with flour mixture, beating until just blended after each addition. Dust toasted pecans with a fine layer of cake flour, fold into batter and stir just to combine; do not over mix.
Scrape batter into prepared pan and and spread evenly. Bake until cake is nicely browned at the edges, springs back when lightly touched at the center and a wooden skewer inserted into the center comes out clean, about 1 hour and 15 minutes. Remove cake from oven and cool in pan on a wire rack for 15 minutes; remove from pan, and cool completely on a wire rack.
To make the icing, using an electric mixer, beat cream cheese and butter in large bowl until smooth. Add the vanilla extract, maple syrup and confectioners'' sugar and beat at low speed until just creamy, do not overbeat. If necessary, adjust syrup or sugar until you achieve the desired consistency. Spread over the cooled cake and transfer to a serving dish.
Makes one 10-inch tube cake, or about 12 servings.
You can use a 12 cup Bundt pan instead of the 10-inch tube pan. Just reduce the oven temperature to 325 degrees F.
Toast nuts (to crisp and bring out their essential oils) prior to adding them into batters; raw nuts are steamed in the batter as it cooks and end up soft and flavorless, toasted nuts are also steamed but retain much of their crunchiness and intensified nutty flavor.
Chopped nuts should be coated with a fine layer of flour before adding them into batters; this helps them distribute more evenly and keeps them from sinking to the bottom
One note about the baking...if in doubt, leave it in longer. An overdone pound cake is preferable to one that is not cooked in the middle.