Keep a wide heavy bottom pan on high heat. Add the peppers to the hot pan and saute on high heat until they are blistered (8-10 minutes). Keep stirring at regular intervals.
Add cumin seeds and whole garlic cloves and mix everything. Cook until garlic cloves are blistered.
Add green chilies and garlic mixture to a large mortar and pestle along with salt to taste and pound to make a coarse paste.
Just make sure to keep it coarse and not pasty.
Thecha is ready to serve.