In a medium saucepan, pour in 2 cups of milk over medium heat. Warm gently until steaming but not boiling, about 5 minutes.

Whisk in 1/4 cup of unsweetened cocoa powder until smooth, about 2 minutes.

Stir in the freshly grated zest of one lemon and let simmer on low for 2-3 minutes.

Add 2-4 tablespoons of sugar, stirring until dissolved for about a minute.

Beat 2 egg whites with an electric mixer on medium speed until soft peaks form, about 2-3 minutes. Gradually add 1/4 cup of powdered sugar, beating until stiff peaks develop.

Pour the hot chocolate into mugs and top with fluffy meringue, creating peaks and swirls.

Optional: Use a kitchen torch to lightly toast the meringue until golden brown.