The recipe:
1/2 cup all purpose flour
2 cups cold water
Combine these two ingredients in a bowl. Add this mixture to a saucepan of 2 cups boiling water and bring it to a boil again. Remove from the heat and stir in 3 tablespoons of sugar. Let it cool; it will thicken as it cools. Once it cools, it's ready to use!
WARNING - it does take at least 2 days to dry. I recommend at least 4 layers of paper for a sturdy pinata!