Step 1
Preheat the oven to 350 degrees F (175 degrees C). Grease or line a 9-inch cake pan with parchment paper.
Step 2
Whisk flour nutmeg baking soda baking powder salt cinnamon and cloves together in a medium bowl. Set aside.
Step 3
Beat sugar and butter together in a large bowl with an electric mixer until light and fluffy. Add eggs one at a time beating well after each addition. Mix in vanilla extract. Add 1/3 of the flour mixture and stir until just combined. Pour in 1/2 of the cream and 1/2 of the spiced rum and mix until just combined. Continue alternating adding the flour mixture cream and spiced rum until combined. Do not overmix. Pour batter into the prepared pan.
Step 4
Bake in the preheated oven until a toothpick inserted into the center of the cake comes out clean 35 to 40 minutes. Allow to cool for 5 minutes in pan before removing to a serving platter.
Step 5
While cake is baking make the eggnog sauce. Whisk egg yolks and sugar together in a small bowl. Mix in flour cornstarch vanilla extract and salt; mixture will be very thick.
Step 6
Combine milk and eggnog in a medium saucepan over medium-low heat. Heat until just barely simmering. Slowly pour 1/2 of the hot milk mixture into the egg yolk mixture whisking constantly. Pour egg yolk mixture back into the saucepan with the milk and eggnog; whisk to combine. Continue cooking whisking constantly until thickened about 2 minutes.
Step 7
Pour sauce through a fine-mesh sieve into a heat-safe bowl. Let cool slightly then place a piece of plastic wrap directly onto the surface of the sauce to prevent a skin from forming.
Step 8
While cake is still very warm poke holes all over using the handle of a wooden spoon. Slowly pour eggnog sauce over cake and let soak in spreading sauce over the cake with a spatula if necessary. Allow to cool completely at least 30 minutes.
Step 9
Make eggnog whipped cream just before serving. Beat cream eggnog powdered sugar vanilla extract and salt together on high speed in a medium bowl until stiff peaks form.
Step 9
Place several dollops of whipped cream on the completely cooled cake. Top with freshly grated nutmeg.