Preheat your oven to 375°F (190°C). Butter 4 ramekins and coat with sugar.

In a mixing bowl, whisk together the egg yolks, sugar, and cornstarch until smooth.

In a saucepan, warm the eggnog with butter, nutmeg, and cinnamon over medium heat.

Gradually whisk the warm eggnog into the yolk mixture. Return everything to the saucepan and cook until thickened. Remove from heat and stir in vanilla extract. Let it cool slightly.

In a clean bowl, beat egg whites until foamy. Slowly add sugar and continue beating until stiff peaks form.

Fold the egg whites into the custard base in three additions, being careful not to deflate the mixture.

Divide the mixture evenly into the ramekins, leveling the tops.

Bake for 15–18 minutes until puffed and golden.

Dust with powdered sugar and serve immediately.