Preheat oven to 325 degrees F (165 degrees C). Grease and flour a 10-inch Bundt pan or tube cake pan. Sprinkle the walnuts evenly in the bottom of the prepared pan.
Place the cake mix, pudding mix, 1/2 cup water, vegetable oil, eggs, and 1/2 cup whiskey into a mixing bowl, and beat until well blended with an electric mixer, about 2 minutes. Pour the batter over the nuts in the pan.
Bake in the preheated oven until the cake is set and the top springs back when pushed slightly, about 1 hour. When the cake is completely cool, run a paring knife between the cake and the edge of the pan. Hold the cake pan on its side and gently tap the sides of the pan against the counter to loosen it. Cover the cake pan with a plate or cooling rack, and invert it to tip the cake out of the pan and onto the plate. Poke holes all over the top of the cake with a toothpick.
To make glaze, melt butter in a saucepan over low heat, then pour in 1/4 cup water and the sugar. Stir the mixture together until smooth, and bring to a boil over medium-low heat; boil for 5 minutes, then remove from heat and stir in 1/2 cup whiskey. Let the mixture cool about 10 minutes, then pour the warm glaze over the cake, allowing it to soak into the holes in the cake.