Grease a 12-cup Bundt pan with 2 Tbsp. shortening, and dust with 2 Tbsp. flour. Set pan aside.
Stir together 2 cups flour, salt, and baking soda in a medium bowl.
Beat 12 Tbsp. butter and next 3 ingredients at medium speed with an electric mixer 3 minutes or until fluffy. Beat in peanut butter and vanilla. Add eggs, 1 at a time, beating until blended after each addition. Gradually add flour mixture, beating at low speed until blended. Stir in 1/4 cup chopped peanuts.
Spoon one-third of batter into prepared Bundt pan. Carefully spoon Filling onto center portion of batter. (Filling should touch edges of pan as little as possible.) Spoon remaining batter over Filling.
Bake at 300° for 1 hour and 30 minutes or until a long wooden pick inserted in center of cake comes out clean. Cool in pan on a wire rack 10 minutes; remove from pan onto a wire rack, and cool 1 hour or until completely cool.
Drizzle Glaze evenly over top of cake, and sprinkle with remaining 1/2 cup chopped peanuts. Chill 2 hours. Serve chilled or at room temperature.