Happens when you fill too much in one pan--should not be more than 1/2 full.
Also when cooked on too high heat, when it cooks outwardly but not inside.

Try the recipe on this url. Use the puffed ones for gol gappa and the rest for paapri chaat:

http://www.niruskitchen.com/recipes/details.asp?recipe_id=550&category_id=43

I have to know the recipe you use before I can comment.

Date chutney
ngredients
Dates 250 g
Powdered ginger (sonth) 1 tsp

Preparation
Soak the dates in water to cover for 3-4 hours.
De-seed the dates and make into a paste in a food processer along with the ginger powder.
Place mixture in a pan and bring to a boil and then simmer for about 5 minutes.

Date chutney
ngredients
Dates 250 g
Powdered ginger (sonth) 1 tsp

Preparation
Soak the dates in water to cover for 3-4 hours.
De-seed the dates and make into a paste in a food processer along with the ginger powder.
Place mixture in a pan and bring to a boil and then simmer for about 5 minutes.