Melt butter in a large saucepan over low heat. Once melted, add in marshmallows and stir until completely melted. Remove from heat.
Stir in Crisp Rice Cereal. Using buttered hands add about ⅓ cup to each muffin tin. Press down in the centre with a pestle to create a pocket. Be careful to leave some mixture at the bottom. Let set for 30 minutes.
Grass:
Add coconut to a small bowl. Add in food colouring and stir until coconut is green. Place about a teaspoonful of grass in each nest.