Using a hand mixer, beat the egg yolks until frothy, then add in the half cup of sugar. Continue to beat until the yolks are pale. Set aside.
Heat the milk, heavy cream, and maple syrup over medium-high heat, until the mixture is just steaming, or about 160°F. The liquids should not be simmering. Add the split vanilla bean, cinnamon stick, and grated nutmeg and stir.
Use a ladle to pour about 1 cup of the warmed dairy mix into the egg yolks. Whisk constantly so as not to scramble the yolks. Once mixed, slowly pour the yolk mixture back into the larger pot, stirring constantly.
Bring the pot to a light simmer for 30 seconds, then remove from the heat. Cool to room temperature, then cover and chill fully.
Once chilled, whip the egg whites until bubbly, then slowly pour in the remaining 2 tablespoons of sugar. Whip until soft peaks form, about 5-8 minutes.
Transfer the whipped egg whites to the chilled base. Stir in the brandy for an alcoholic version. Mix to the desired consistency - for an authentic Astrid-style yaknog, only mix about halfway so that the drink is thick and has 'chunks' of egg white throughout. Serve immediately and enjoy!