Marshmallow Chocolate Cake

Recipe:
- Chocolate cake:
+ 100g Unsalted Butter
+ 75g Sugar
+ 2 eggs
+ 130g All-purpose flour
+ 1 tsp Baking powder
+ 20g Cocoa powder
+ Bake at 170 for 12 minutes (Bake at 170℃ for 12 minutes)
+ Chocolate
+ Hot water
- Marshmallows:
+ Low heat
+ 50g Unsalted Butter
+ 120g Marshmallows
+ 15g Milk powder