Mix instant coffee, 3 tablespoons of sugar, and water in a tall jar.
Mix with a handheld mixer until thick. Set aside.
Eggnog Dalgona
Heat milk, heavy cream, sugar, vanilla, and nutmeg in a saucepan over medium high heat.
In a seperate bowl, mix egg yolks with a whisk.
When the milk mixture gets hot, take 1/3 of a cup of the hot milk mixture and slowly pour it into the yolk mixture. Whisk quickly, until the hot milk is incorperated with the yolks. Repeat this step until you've transfered about 1.5 cups of hot milk into the yolk mixture.
Pour the milk and egg yolk mixture back into the sauce pan and whisk vigorously. Once heated, remove from heat and pour.
If serving hot, top with dalgona and serve.
If chilling the eggnog, put in the fridge and top with the dalgona before serving.