How to Make It
Preheat oven to 350ºF. Beat butter with an electric mixer on medium speed until smooth, about 1 minute. Slowly add granulated sugar, beating until combined, about 2 minutes. Add eggs, 1 at a time, reducing speed to low to add each egg and increasing to medium speed for 30 seconds after each addition. Beat on medium for 1 minute after adding last egg.
Whisk together flour, salt, and nutmeg in a medium bowl. Stir together cream, 1/4 cup of the bourbon, and 1 tablespoon of the vanilla in small measuring cup. With mixer running on lowest speed, add flour mixture and cream mixture to butter mixture in batches, beginning and ending with flour mixture, beating until just blended after each addition and stopping to scrape bowl as needed. Transfer batter to a greased (with shortening) and floured 12- to 15-cup Bundt pan. (If using a 12-cup pan, cake may bake above rim; trim as needed to level.)
Bake in preheated oven until a toothpick inserted in middle of cake comes out clean, 1 hour to 1 hour, 10 minutes. Let cake cool in pan on a wire rack until pan is just cool enough to handle, 20 minutes. Turn cake out onto rack to cool, 1 hour.
Stir together powdered sugar, 2 tablespoons of the eggnog, and remaining 1 tablespoon each bourbon and vanilla in a large bowl until smooth, adding remaining 1 tablespoon eggnog, 1 teaspoon at a time, if needed for desired consistency. Transfer cooled cake to a platter; pour eggnog mixture over cake. Sprinkle with nutmeg; let stand 5 minutes before slicing.