Mix 1/2 cup of the water with the gelatin in a large mixing bowl. Let sit for 10 minutes, allowing to bloom.
In a small saucepan over medium heat, mix the other 1/2 cup of water and sugar and bring to a low boil. Allow sugar to dissolve completely and remove from heat.
Add vanilla extra to water/gelatin mixture. Turn on mixer to low setting and slowly add in sugar/water mixture.
Mix on low for two minutes until fully combined. Increase speed to high for 5-8 minutes until a marshmallow consistency forms.
Melt butter on low heat in a large pot. Add prepared marshmallow batter and stir. Remove heat. Slowly add in cocoa cereal while stirring continuously.
Once mixed completely, spread mixture into greased casserole dish.