In a pan over medium heat, sauté the green chilies with a teaspoon of oil.
Next, add in the garlic and cumin seeds and continue cooking.
Now add in the peanuts and cook for a few more minutes, until the peanuts turn aromatic.
Remove from heat, let cool and transfer to a blender jar with salt. Blitz for a few minutes until you get a coarse paste.
Notes
Use a good quality heavy bottomed pan or a cast iron skillet to roast the chilies and peanuts. Cook them over medium-low flame and keep stirring, so they don't end up burning.
To tone down the spiciness of the thecha, you can choose to de-seed the green chilies and use a sharp knife to scrape off the white pith on the inside.
You may also want to wear gloves while handling the chilies. If you're using spicy chilies, your hands may burn after chopping them.
I used peanuts with their skin on here. You can choose to de-skin them too, if you want to. Just remember to pan roast them first, allow them to cool down and then de-skin them.
Traditionally, the thecha is ground using a mortar and pestle, and if you have one, I would highly recommend using it. I used a blender because I just found it more convenient.