1. Preheat oven to 350 degrees F. Butter a 9-inch springform pan or pie pan. Set aside.
2. Whisk together flour, baking powder, salt, cinnamon, and nutmeg in a medium bowl. Set aside.
3. In the bowl of a stand mixer, beat the butter and sugar until pale and fluffy, about 3 minutes. Add in egg, eggnog, vanilla, and rum extract. Mix until combined.
4. Gradually mix in the dry ingredients. Transfer batter to prepared pan.
5. To make the streusel topping, in a small bowl stir together flour, brown sugar, cinnamon, and nutmeg. Add in butter pieces and mix together with your fingers until crumbly. Top the cake with streusel. Sprinkle white chocolate chips evenly over the cake.
6. Bake cake for 40 minutes or until cake is golden brown and firm to the touch. Let cool in pan for 15 minutes. Remove from pan and cool completely on a wire cooling rack.
7. While the cake is cooling, make the eggnog glaze. In a medium bowl, whisk together powdered sugar, eggnog, rum extract, and nutmeg. Drizzle glaze over cooled cake. Cut into slices and serve.
Note-the cake will keep up to 2 days, stored in an air-tight container on the counter.